Kidney and Ureter

Nephrectomy may be indicated by the following unilateral conditions: 1) solitary renal cysts causing serious renal dysfunction; 2) hydronephrosis; 3) polycystic disease of the kidney complicated by pyelonephritis refractive to medical treatment; 4) infestation by Dioctophyma renale with severe degenerative changes; 5) neoplasms of the kidney if metastasis has not occurred; 6) traumatic destruction of most of the renal parenchyma; 7) avulsion of the renal pedicle or uncontrolled hemorrhage; and 8) abnormal kidney drained by an ectopic ureter. The diagnosis of these conditions and assessment of adequate function of the contralateral kidney are described elsewhere.¹

Nephrectomy is seldom performed when the architecture and vascular supply of the kidney are normal. In certain chronic pathologic states, the kidney is frequently enlarged and is extensively supplied by neovascularization. The normal renal artery and vein can be present or nonexistent. Surgical technique for nephrectomy in such instances is improvised by the veterinary surgeon and may approximate the dissection required to remove any abdominal mass. The operative technique described in the following paragraphs is based on the removal of a kidney in which the gross anatomic structure is recognizable.

Surgical Technique

The patient is anesthetized and is placed in dorsal recumbency. The abdomen is prepared for an aseptic surgical procedure. A midline abdominal incision is made from the xiphoid process through the umbilicus. The edges of the incision are protected with moist laparotomy pack, and a Balfour retractor is inserted.

The right kidney is exposed by lifting the descending portion of the duodenum and by positioning the other loops of intestine to the left of the mesoduodenum. The left kidney is similarly exposed by using the mesentery of the descending colon as a retractor to displace bowel loops to the right (Figure 29-1). The viscera are covered with moist laparotomy packs.

To mobilize the kidney to be removed, first the peritoneum over the caudal pole of the kidney is grasped with tissue forceps and is incised with scissors. The surgeon inserts a finger into the opening and gently peels the peritoneum from the kidney. Occasionally, the peritoneum adheres firmly to the kidney surface at scattered points; these attachments are severed with scissors. Bleeding generated by this reflection of the peritoneum is controlled by electrocautery. Perirenal fat is reflected from the ventromedial surface of the renal hilus to expose the renal vein and ureter. The ureter is further mobilized by dissection through the retroperitoneum, to permit ligation as close to the urinary bladder as feasible. The ureter is divided between 2-0 absorbable ligatures (Figure 29-2).

The kidney is lifted from its bed and is retracted medially to 1 expose the perirenal fat on the dorsolateral surface of the renal hilus (See Figure 29-2). Reflection of this fat exposes the renal artery. Care must be taken to avoid transection of one or more branches of the renal artery that may be present.

The exposed renal artery and vein are separated and are independently Iigated with 3-0 suture material (Figure 29-3). The artery and vein are transected distal to each ligature, and the kidney is removed. A separate suture ligature of 4-0 suture material is passed through the lumen of the renal artery and vein, distal to the first ligature, to transfix the distal ligature and to prevent retraction of the vessel from the ligature (Figure 29-4).

The intestines are returned to normal position, the greater omentum is repositioned over the small intestine, and the abdomen is closed in a standard manner.
 

Reference

1. Osborne CA, Finco DR, eds. Canine and feline nephrology and urology. Baltimore: Williams & Wilkins, 1995.
    

Surgical Anatomy

Kidneys and ureters lie against the sublumbar muscles of the dorsolateral abdomen within the retroperitoneal space. The cranial pole of the right kidney is nestled in the renal fossa of the caudate liver lobe at the approximate level of the 13th rib (slightly cranial to the left kidney). A thin fibrous capsule envelopes each kidney. Gross appearance of the feline kidney is distinctive due to a radial network of subcapsular veins that course over the surface of the kidney toward the hilus.

The renal artery, vein, and ureter enter the concave surface of the kidney at the hilus (Figure 29-5). The primary renal artery may arborize into several branches after leaving the aorta and before entering the hilus. Arterial branching is present in 5 to 10% of dogs and cats and is most common in the left kidney. Cats may also have multiple renal veins. The left testicular or ovarian vein drains into the left renal vein rather than the caudal vena cava. Care must be taken to preserve these vessels when performing renal surgery in an intact dog or cat. The ureter is a firm tubular structure that exits the caudodorsal surface of each kidney at the hilus and courses in a caudal direction in the retroperitoneal space. The left ureter courses lateral to the aorta, but the right may be dorsal or lateral to the vena cava. In male dogs and cats, the ureter crosses dorsal to the ductus deferens and in the female it courses in the dorsal aspect of the broad ligament.¹⁷ Each ureter traverses the respective right or left lateral ligament of the urinary bladder and enters the bladder on the dorsolateral mucosal surface at the trigone.
 

Traditional surgical approach to the kidneys and ureters is via a ventral midline celiotomy. The left kidney is exposed by grasping and retracting the colon and associated mesocolon across midline toward the right side (Figure 29-6). The right kidney is similarly exposed by grasping and retracting the duodenum and associated mesoduodenum toward the left side (Figure 29-7). Gentle retraction of the duodenum is recommended to minimize trauma to the pancreas.
 

Preoperative Assessment of Renal Function

Kidney function can be estimated from serum blood urea nitrogen (BUN) and creatinine (SCr) levels, but these biochemical markers are relatively insensitive. The BUN and SCr levels should be interpreted concurrently with a urinalysis and urine specific gravity. Urine specific gravity is most accurate when obtained prior to initiation of fluid therapy. Measurement of BUN and SCr levels are the simplest methods of evaluating renal function in the clinical patient however elevation of values beyond the normal range does not occur until severe kidney disease is present (less than 30% functional nephrons remaining). An additional limiting factor is that biochemical markers only provide information regarding total renal function and do not provide specific quantification of individual kidney function. Assessment of individual kidney function is important when trying to determine whether efforts to preserve a kidney via nephrotomy or pyelolithotomy should be considered or if nephrectomy is indicated. Determination of glomerular filtration rate (GFR) is essential in dogs and cats with underlying renal disease to guid specific treatment recommendations and provide prognostic information.

Scintigraphy is a reliable, non-invasive method of assessing total and individual kidney function in the dog and cat. Renal function is determined though measurement of GFR of labeled radioisotopes.¹ Normal total GFR in dogs is greater than 3 ml/min/kg; in cats, normal total GFR is greater than 2 ml/min/kg. Quantitative renal scintigraphy also measures individual kidney function and is sensitive enough to detect changes in function before BUN or SCr increase. Scintigraphic assessment of GFR using 99 m Technetium-diethylenetriaminepentaacetic acid (99 mTc-DTPA) correlates well with other methods of assessing renal function in the dog and cat.^2,3 The use of scintigraphy may be limited by availability and requires isolation of the patient while the radioactive material is cleared and reaches safe levels for human exposure.

Glomerular filtration rate can also be determined using contrast-enhanced computed tomography (CT). Collection of serial CT images of specific regions of interest for the kidneys and aorta permits construction of time attenuation curves that can be used to calculate GFR using graphical analysis. Tomography also provides morphologic information of the kidneys and ureters. CT use is limited by availability and the need for general anesthesia of the patient.^14-15

Survey radiographs, excretory urography, and ultrasonography are valuable in evaluating renal and ureteral size and architecture. Location and number of urinary calculi may be determined through radiographs or ultrasound. Excretory urography can be used to evaluate the anatomy and patency of the urinary system but is not accurate in quantitative assessment of kidney function. Selection of diagnostics is based on the specific clinical problem and availability of imaging modalities.

Results of preoperative diagnostics may influence the anesthetic protocol, guide surgical planning, and aid in determining prognosis. Dogs and cats with normal renal function that receive appropriate perioperative intravenous fluids usually adjust to temporary changes in cardiovascular function and renal perfusion during anesthesia, however, patients with decreased renal function may not be able to adjust to these changes and could develop serious postoperative complications (i.e. acute renal failure). Fluid therapy should be carefully monitored, especially in cats, to avoid fluid overload. Preoperative assessment of renal function is important to reduce risk of postoperative complications and to provide the most accurate prognosis for expected outcome following surgery.

Other perioperative considerations include administration of fluids, diuretics, or vasopressors to support kidney function and maintain urine output. Intraoperative and postoperative urine output and central venous pressure monitoring should be considered especially in animals with preexisting renal disease. Electrolyte levels, body weight, and hydration status should be closely monitored.¹⁵

Surgical Technique

Indications for renal surgery include neoplasia, obstructive renal calculi, trauma, persistent renal hemorrhage, chronic inflammation or infection, severe hydronephrosis, renal cystic disease and in some cases, treatment of ectopic ureters.⁴ Appropriate preoperative diagnostics and careful assessment of the patient will guide the clinician in formulating an overall treatment plan.

Nephrotomy

Nephrotomy is most commonly performed to remove obstructive or infected calculi but is also indicated to evaluate the renal pelvis for causes of hematuria or chronic infection, or to biopsy tumors. It is important to recognize that not all nephroliths require surgical removal. Nephrotomy or pyelolithotomy for urinary calculi is indicated when there is evidence of urinary obstruction or chronic infection. Historically, bisection nephrotomy was thought to decrease renal function by 20 to 50% in normal dogs however, more recent studies have reported that nephrotomy has no significant adverse effect on renal function in the normal dog or cat.^5-9 The effect of nephrotomy on renal function in patients with kidney disease has not been reported.

To perform nephrotomy, a ventral midline celiotomy is routinely used. A generous incision extending from the xiphoid to a few centimeters caudal to the umbilicus is recommended. Moistened laparotomy sponges are placed over the edges of the abdominal wall and self-retaining Balfour retractors are used to maintain abdominal exposure. The left or right kidney is exposed as previously described. Exposure of either kidney can be maintained or improved by use of laparotomy sponges and malleable retractors held in place by a sterile surgical assistant. Peritoneum overlying the kidney is incised and the kidney is bluntly dissected from peritoneal and fascial attachments. Perihilar fat is carefully dissected to expose the renal artery, vein, and ureter (Figure 29-8). The renal artery is often difficult to visualize since it lies craniodorsal and is intimately associated with the renal vein, however it is generally easily palpated. Careful dissection continues until the renal artery can be isolated. Once the artery is adequately exposed, it is temporarily occluded with either a Rumel tourniquet or a vascular clamp (i.e. Bulldog clamp) placed near the aorta. Successful renal arterial occlusion is confirmed by gross blanching of renal color and palpable softening of the parenchyma. The kidney is grasped gently to stabilize it as an incision is made with a scalpel blade along the convex surface (approximately one-half to two-thirds the length of the convex surface). Blunt and sharp dissection of the renal parenchyma is continued to the pelvis (Figure 29-9). Arcuate vessels located within the parenchyma can be ligated if necessary, but bleeding is usually minimal if all branches of the renal artery have been occluded. Once the renal pelvis is exposed, samples can be collected as indicated for histopathology, culture, and mineral analysis. A 3.5 or 5.0 Fr red rubber catheter can be passed normograde into the proximal ureter and gently flushed with warm sterile saline to confirm ureteral patency (Figure 29-10). Once all samples have been collected and/or calculi removed, the bisected renal parenchyma is held gently but firmly in apposition as the capsule is closed.
 

A simple continuous pattern using 4-0 or 5-0 monofilament absorbable suture on a taper needle is generally effective at providing satisfactory closure and hemostasis. Sutures bites are placed 2-3 mm apart in the fibrous capsule to minimize tension and tearing. Renal cortical tissue is occasionally included in suture placement if the capsule tears or does not hold suture adequately (Figure 29-11). Once the capsule is closed, the vascular occlusion device is removed and normal kidney color and parenchymal consistency promptly return. Total vascular occlusion of the kidney during nephrotomy should not exceed 15 to 20 minutes.¹⁰ If hemorrhage occurs from the sutured incision it can be controlled with direct digital pressure or placement of a mattress suture(s) through cortical tissue at the level of hemorrhage. After hemostasis is obtained, the kidney is returned to its normal position and orientation within the abdomen; tacking sutures between each pole of the kidney and the sublumbar musculature may be necessary to prevent kidney rotation that could cause occlusion of the renal vasculature or ureter. Samples should be submitted for culture, histologic examination, and mineral analysis as indicated. The abdomen is lavaged with warm sterile saline and closure is routine. Sponge counts are recommended before abdominal closure to ensure nothing is inadvertently left in the abdomen. If bilateral nephrotomies are necessary, the procedures should be staged at 4 week intervals to lessen the risk of postoperative acute renal failure or decompensation.¹²
 

Pyelolithotomy

Pyelolithotomy is an alternative to nephrotomy and can be used to remove calculi from the renal pelvis if the proximal ureter is sufficiently dilated. Extracorporeal shock wave lithotripsy may also be considered to treat dogs with small nehroliths (< 1-2 cm).¹⁶ Excretory urography, ultrasonography and scintigraphy can be used to confirm and estimate the severity of obstruction of the renal pelvis or ureter. In cases of ureteral obstruction, placement of a nephrostomy tube or ureteral stenting may be warranted prior to definitve treatment or as adjunctive treatment.¹⁵

The ureter exits the caudodorsal aspect of the renal hilus and may be obscured by overlying vessels and preihilar fat. Adequate exposure is generally obtained from the ventral surface of the hilus, but if necessary, the kidney can be elevated from the peritoneal attachments and rotated medially to expose the dorsal surface. Vascular occlusion of the kidney is not necessary during pyelolithotomy. The ureter is isolated by blunt dissection and a longitudinal incision is made over the renal pelvis extending along the proximal ureter. An 11-blade and iris scissors may facilitate pyelolithotomy; magnification is also extremely helpful, especially when operating cats or small dogs. The length of the ureteral incision should be adequate to allow the calculus to be gently removed without tearing tissues or fragmenting the calculus (Figure 29-12). After removing the calculus, a 3.5 Fr red rubber catheter should be passed proximally into the renal pelvis and distally into the ureter to gently flush any remaining calculi fragments (Figure 29-13). The catheter may be used to temporarily aid the surgeon to visualize ureteral tissue layers as the pyelolithotomy is closed. It is important to appose tissues accurately to avoid stricture or urine leakage at the surgical site. Absorbable monofilament 4-0 or 5-0 suture in a simple continuous pattern is recommended (Figure 29-14). If peritoneal attachments between the kidney and abdominal wall were disrupted during dissection, the kidney should be pexied to the abdominal wall as previously described. Samples should be submitted for histologic examination, calculus analysis, and culture as indicated. Closure of the abdomen is routine.
 

References

1. Daniel GB, Mitchell SK, Mawby D, et al.: Renal Nuclear Medicine: A Review. Vet Radiol Ultrasound 401: 572, 1999.
2. Uribe D, Krawiec D, Twardock A, et al.: Quantitative renal scintigraphic determination of the glomerular filtration rate in cats with normal and abnormal kidney function, using 99mTc-diethylenetriaminepentaacetic acid. Am J Vet Res 53: 1101, 1992.
3. Krawiec DR, Badertscher RR, Twardock AR, et al.: Evaluation of 99mTc-diethylenetriaminepentaacetic acid nuclear imaging for quantitative determinationof the glomerular filtration rate of dogs. Am J Vet Res 47: 2175, 1986.
4. Rosin, E: Kidney – Nephrectomy In Bojrab MJ, 4th ed: Current Techniques in Small Animal Surgery. Maryland: Williams and Wilkins, 1998, p 429.
5. Gahring DR, Crowe DT, Powers TE, et al.: Comparative renal function studies of nephrotomy closure with and without sutures in dogs. JAVMA 171: 537, 1977.
6. Fitzpatrick JM, Sleight MW, Braack A, et al.: Intrarenal access; Effects on renal function and morphology. British J of Urology 52: 409, 1980.
7. Stone EA, Robertson JL, and Metcalf MR: The effect of nephrotomy on renal function and morphology in dogs. Vet Surgery 31: 391, 2002.
8. Zimmerman-Pope N, Waldron DR, Barber DL, et al: Effect of fenoldopam on renal function after nephrotomy in normal dogs. Vet Sug 36: 566, 2003.
9. King M, Waldron DR, Barber DL, et al.: The effect of nephrotomy on renal function and morphology in normal cats. Ver Surg 35: 749-758, 2006.
10. Selkurt EE: The changes in renal clearance following complete ischemia of the kidney. AM J Physiol 144: 395-403, 1945.
11. Maddern JP: Surgery of the Staghorn Calculus. Brit J Urol 39: 237, 1967.
12. Rawlings CA, Bjorling DE, Christie BA: Kidneys In Slatter D, 3rd ed.: Textbook of Small Animal Surgery, Philadelphia, 2002, p 1606.
13. Alexander K, Dunn, M, Carmel EN, et al: Clinical application of Patlak Ploty CT-GFR in animals with upper urinary tract disease. Ver Radiol Ultrasound 47 (2), 127-135,2006.
14. Anderson KJ,Twardock R, Grimm JB, et al: Determination of glomrular filtration rate in dogs using contrast-enhanced computed tomgraphy. Vet Radiol Ultrasound 47 (2), 86-103,2011.
15. Berent AB: Ureteral obstructions in dogs and cats: a review of traditional and new interventional diagnostic and therapeuitc options. J Vet Emerg Crit Care 21 (2), 86-103,2011.
16. Lane IF: Lithotripsy: an update on urologic applications in small animals. Vet Clin NA Small Animal Pract 34 (4): 1011-1025,2004.
     

Introduction

The location and composition of uroliths in cats has changed dramatically over the past three decades. Between 1981 and 1999 there was a dramatic increase in the number of upper tract uroliths submitted to the Minnesota Urolith Center.¹ Approximately 75% of upper tract uroliths are composed of calcium oxalate.¹ During this 20-year period there was a 10-fold increase in the frequency of upper tract uroliths in cats at nine veterinary teaching hospitals.¹ A more recent case series of cats treated for ureterolithiasis found that approximately 98% of ureteroliths contain calcium oxalate.² Veterinary surgeons are increasingly faced with the challenge of surgical management of upper tract uroliths in cats.

Clinical Signs

Clinical signs of cats with ureteroliths or nephroliths tend to be nonspecific and include anorexia, vomiting, lethargy, and weight loss.² Polydipsia and polyuria, stranguria or pollakiuria, hematuria, and inappropriate urination may be seen. Pain may be evident if the ureter becomes acutely obstructed, however, pain appears to be much less common than in humans with ureteroliths. Affected cats may be asymptomatic and the calculi are detected during a work-up for other problems. Many cats with ureteroliths and nephroliths also have chronic kidney disease, therefore, unilateral ureteral obstruction may result in signs of renal failure. Physical examination findings are usually non-specific, but some cats will have small, irregularly shaped kidneys. Acute ureteral obstruction may result in the affected kidney being enlarged, firm, and painful.

Diagnosis and Preoperative Evaluation

Nephroliths and ureteroliths should be suspected in cats with chronic kidney disease, renomegaly, abdominal or lumbar pain, vomiting, or recurrent urinary tract infection. Cats that are presented with vague signs of illness or signs of renal disease should be evaluated for the presence of uroliths by survey abdominal radiographs and abdominal ultrasonography. Most uroliths of the upper urinary tract in cats are radiodense and can be seen on survey radiographs. However, calculi can be quite small and may be obscured by fecal material or other structures. It is common to find that one kidney is small and irregular in contour while the other kidney may be of normal size or enlarged. Ultrasonography is very helpful in confirming the presence of calculi and in assessing the degree of dilation of the renal pelvis and ureter. However, ultrasonography failed to identify ureteroliths in 23% of cats in one report.² The combination of abdominal radiographs and ultrasonography is reported to have a sensitivity of 90% for detection of ureteroliths in cats.² Excretory urography can be helpful in identifying ureteral obstruction, assessing the degree of dilation of the renal pelvis and ureter, and determining the tortuosity of the ureters in preparation for surgery. However, many cats with ureteral obstruction do not concentrate the intravenously administered contrast medium adequately to delineate the ureters. In these cats, a percutaneous antegrade pyelogram can be performed. Contrast medium is injected directly into the renal pelvis using ultrasound guidance and radiographs are made of its passage down the ureter.^3,4 The technique also allows a urine sample to be obtained directly from the renal pelvis for bacterial culture.

A complete blood count (CBC), serum chemistry profile, and urinalysis should be performed to evaluate renal function and the cat’s general health. A CBC may show a nonregenerative anemia if the cat has chronic renal failure; a leukocytosis and left shift may be present in cats with pyelonephritis. A serum chemistry profile may be normal or may show azotemia, hyperphosphatemia, and hyperkalemia. An idiopathic hypercalcemia is reported to occur in approximately 35% of cats with calcium oxalate uroliths.⁵ A urinalysis and urine culture should be performed to determine if there is a urinary tract infection. If surgery is planned, a cross-match or blood typing should be performed in case administration of blood is needed during or after surgery. Compatible whole blood or packed red cells should be available.

Indications for Surgery

Indications for surgical removal of nephroliths and ureteroliths in cats are controversial. In general, nephroliths that are not associated with a urinary tract infection and that are not causing ureteral obstruction do not require surgical removal. However, if a cat with nephroliths has a urinary tract infection that cannot be cleared with appropriate antimicrobial therapy, then surgical removal of the nephroliths is recommended to allow clearance of the bacteria. If a nephrolith is causing complete or partial obstruction of urine flow, removal is indicated. Nephroliths that appear quiescent are generally not removed because the consequences of surgical removal are renal scarring and possible reduced renal function. In addition, it can be quite difficult to locate small nephroliths by nephrotomy or pyelolithotomy. If bilateral nephrotomies are required, the procedures should be staged with the nephrotomies separated by approximately 4 weeks. In general, the kidney that appears to have the most functional capacity should be operated first. Pyelolithotomies can be performed bilaterally at the same surgery.

There are no clear recommendations regarding surgical removal of ureteroliths in cats. Most ureteroliths cause some degree of obstruction of the ureter. Prolonged ureteral obstruction can lead to renal damage and loss of function. If a cat with a ureterolith is treated conservatively to allow the calculus to pass spontaneously, there is a chance of further loss of renal function during the weeks or months that it may take for passage, if passage of the calculus ever occurs. One study showed that resolution of ureteral obstruction occurred in very few cats treated with medical therapy alone.¹⁰ It has not been determined if there is a “safe” waiting time for conservative management of ureteroliths in cats. The overall status of the cat’s renal function should be considered in determining whether conservative or surgical therapy will be pursued. Many cats with nephroliths and/or ureteroliths are azotemic and have chronic kidney disease. Assessment of individual kidney function by nuclear scintigraphy is useful in cats with upper urinary calculi however this diagnostic aid is not widely available. If a cat has a ureterolith in one ureter and the other kidney has end-stage renal disease, surgical removal of the ureterolith is recommended to preserve the function of the obstructed kidney. If the cat is very ill due to ureteral obstruction by a ureterolith, it may not be appropriate to wait for the ureterolith to pass. As I have gained experience with ureteral surgery in cats, I have become more aggressive in pursuing surgery sooner rather than later. This is consistent with another report.¹⁰ Aggressive fluid therapy is administered to stabilize the cat while monitoring the cat carefully for fluid overload. If the ureteral obstruction persists, surgical intervention is usually performed in 2-4 days. If bilateral ureterotomies are necessary, they can be performed in the same surgery.

Many cats with ureteroliths have concurrent nephroliths. Following ureterotomy, these cats are at risk for recurrent ureteral obstruction by nephroliths that may pass into the ureter. Because of this, ureterotomy is now generally reserved for cats with a single ureterolith and no nephroliths. Cats with multiple ureteroliths and nephroliths are generally being treated with ureteral stenting or subcutaneous ureteral bypass (SUB) placement.⁶ Ureteral stenting results in dilation of the ureter so that urine can pass around and through the stent thus relieving the obstruction and preserving renal function. SUB placement allows urine to be diverted from the renal pelvis to the urinary bladder through a combination of a locking-loop nephrostomy catheter and a locking-loop cystostomy catheter.⁶

Surgical Treatment

Nephroliths

Nephroliths can be removed by either nephrotomy or pyelolithotomy. With either technique, however, it is not always possible to retrieve all the calculi. Nephrotomy should be avoided when possible because it can cause renal scarring and loss of function. Many cats with nephroliths already have reduced renal function and further loss of function should be avoided. Pyelolithotomy is the preferred technique for surgical removal of nephroliths because it does not require interruption of renal blood flow or incision into the renal parenchyma and the resulting loss of function. However, pyelolithotomy cannot be performed unless the renal pelvis is dilated beyond the renal parenchyma. If a kidney is severely hydronephrotic and non-functional, nephrectomy and ureterectomy are indicated.

All retrieved nephroliths and ureteroliths should be submitted for quantitative analysis so that appropriate preventative strategies can be implemented. Bacterial culture should also be performed on any calculi that are available.

Nephrotomy

After performing a complete abdominal exploratory, the kidney is packed off from the rest of the abdomen. The peritoneum is incised along the greater curvature of the kidney and the kidney is reflected medially. The renal artery is located on the dorsal aspect of the renal hilus, the renal vein is ventral and the ureter is caudal. The renal artery is isolated by careful dissection and a bulldog vascular clamp is applied. It is not necessary to occlude the renal vein. The kidney should become soft and dark-colored if the entire arterial supply has been occluded. If the kidney does not become soft, the clamp should be removed and further dissection performed to identify additional branches of the renal artery. After occluding the renal arterial supply, a longitudinal incision is made through the renal capsule along the greater curvature for approximately two-thirds the length of the kidney. The renal parenchyma is separated by pushing the blunt handle of a scalpel through the tissue toward the renal pelvis. Once the renal pelvis is reached, the parenchyma is spread so that calculi in the pelvis can be visualized. Calculi are removed, the diverticula are explored for additional calculi, and the renal pelvis is flushed with saline. The ureter is catheterized and flushed to the bladder if possible to confirm its patency. The edges of the kidney are pressed together and the renal capsule is carefully closed with a simple continuous suture of 4-0 polydioxanone. The vascular clamp is removed from the renal artery and direct pressure is applied to the suture line to control hemorrhage as necessary. The warm ischemia time of the kidney should not exceed 20 minutes.⁶ The kidney is tacked in place with a few capsular sutures to the surrounding psoas musculature to prevent the kidney from twisting on its blood supply and causing renal ischemia.

Pyelolithotomy

Magnification is helpful for performing pyelolithotomy in cats. I prefer to use an operating microscope unless the renal pelvis and proximal ureter are extremely dilated. The kidney is reflected medially and the dilated renal pelvis and proximal ureter are exposed by dissecting the perirenal fat away from the ureter at the caudal aspect of the renal hilus. A stay suture of 5-0 to 7-0 suture is placed in the dilated pelvis and a #11 blade is used to make a stab incision into the exposed pelvis. The incision is extended longitudinally with iris scissors. Calculi are retrieved from the renal pelvis and proximal ureter and the renal pelvis is flushed by passing a catheter through the ureteral/ pelvic incision and up into the renal pelvis. If possible, the ureter should be flushed distally to the bladder to assure patency, however, this is not always possible due to the small diameter of the normal feline ureter. The pyelolithotomy is closed with full-thickness simple interrupted sutures of 5-0 to 7-0 polyglactin 910 or polydioxanone. The kidney is tacked in place to surrounding psoas musculature with a few capsular sutures.

Ureteroliths

Ureteral calculi can be removed by ureterotomy or partial ureterectomy and ureteroneocystostomy. Both procedures are technically demanding because of the small size of the feline ureter and should be performed using an operating microscope. Surgeons should have experience with microsurgical techniques and microsurgical instrumentation should be used to avoid unnecessary trauma to the ureter. Because of the difficulties associated with ureteral surgery in cats, some surgeons recommend that ureteroliths located in the middle or distal thirds of the ureter be treated by resection of the portion of the ureter from the calculus to the bladder to remove the calculus and reimplantation of the proximal ureter into the urinary bladder. I prefer to perform ureterotomies for all ureteroliths regardless of location. I reserve partial ureterectomy and ureteroneocystostomy for treatment of complications that could occur secondary to ureterotomy, such as ureteral stricture. Abdominal radiographs should be made immediately before surgery to confirm the current location of the calculi.

Ureterotomy

The ureter is examined visually using the preoperative radiographs to help locate the ureterolith. In many cases the calculus can be seen through the wall of the ureter. The ureter can be palpated gently to identify the ureterolith. If the calculus is located in the proximal ureter, care should be taken not to push the calculus back into the renal pelvis. To prevent the calculus from moving retrograde into the renal pelvis, a loop of moistened umbilical tape or a vascular tie can be placed around the most proximal aspect of the ureter immediately distal to the renal pelvis and the ureter can be gently occluded by applying pressure to the vascular tie. After the ureterolith is identified, the peritoneum is incised over the affected area of the ureter and the periureteral fat is dissected to expose the ventral aspect of the ureteral wall. The operating microscope is positioned over the ureter and a stay suture of 8-0 suture material is placed in the ureter at one end of the planned ureterotomy. A #11 blade is used to make a longitudinal incision into the ureter directly over the calculus and the incision is extended with microsurgical dissecting scissors. The calculus is removed and the ureter is flushed proximally and distally (if possible). If the ureter is very dilated, it can be flushed proximally with a 3.5 French tom cat catheter. If the ureter is not very dilated, a 27-gauge intravenous catheter can be used for flushing. It is often difficult to flush the distal segment of the ureter due to its small diameter. Some surgeons confirm patency of the ureter by passing a piece of suture material (size 2 polybutester⁷) down the ureter. I usually try to flush the distal ureter gently and palpate it carefully to be sure there is not another calculus more distally, but I do not usually pass anything down the ureter to avoid further trauma. A swab is taken from the ureter and/or calculus for aerobic bacterial culture and susceptibility testing. The ureterotomy is closed with full-thickness simple interrupted sutures of 8-0 polyglactin 910 with a BV130-4 taper needle (8-0 Coated VICRYL, Ethicon Inc, Somerville, NJ). In some cases the ureter is very thickened and fibrotic and it is difficult to pass the needle of the 8-0 polyglactin 910 through the wall. In those cases, 7-0 polydioxanone on a BV1 taper needle (PDS II, Ethicon Inc, Somerville, NJ) can be used. It is helpful to preplace the last two or three sutures to ensure proper suture placement. The final sutures are then tied. The suture line should be examined carefully under the operating microscope for urine leakage between sutures or through the needle holes. If urine leakage occurs between sutures, additional sutures should be placed. If urine leakage occurs through the needle holes, a small piece of absorbable gelatin sponge (Gelfoam^®, Pharmacia and Upjohn Company, Kalamazoo, MI) soaked with the patient’s blood can be placed over the suture line. After the ureterotomy is closed, the peritoneum can be closed over the site. However, if closure of the peritoneum compresses the distal ureter so that it causes a partial obstruction, the peritoneum can be left open. If calculi are present in more than one location in the ureter, multiple ureterotomies can be performed at the same surgery. It is not usually possible to flush or milk calculi to a ureterotomy site that is more than a couple millimeters from the calculus unless the ureter is very dilated.

Partial Ureterectomy and Ureteroneocystostomy

Ureteroliths in the distal two-thirds of the ureter may be managed by resecting the ureter from the site of the calculus to the urinary bladder and then reimplanting the ureter into the bladder.⁷ The ureter is ligated and transected proximal to the obstructing ureterolith and at its entry into the urinary bladder and the excised portion is removed with the calculus. The proximal portion of the ureter is implanted into the urinary bladder. Multiple techniques have been attempted for ureteroneocystostomy in cats but the best results occur with an extravesicular mucosal apposition technique (modified Lich Gregoir technique) using simple interrupted sutures.⁸ This technique is performed by making a partial thickness incision through the serosa, muscularis, and submucosa of the ventral aspect of the apex of the urinary bladder to expose the mucosa. The distal end of the ureter is spatulated. An incision equal in length to the spatulated ureteral incision is made through the bladder mucosa at the caudal end of the muscularis incision. One suture is placed between the cranial end of the spatulation and the cranial end of the bladder mucosal incision. A second suture is placed between the distal end of the ureter and the caudal end of the mucosal incision. These sutures are placed full-thickness through the ureter and the bladder mucosa and tied. Then a stent of 4-0 polypropylene is placed in the ureteral lumen to aid in the placement of additional sutures. Two simple interrupted sutures are preplaced between the ureter and the bladder mucosa on one side of the stoma and then two similar sutures are preplaced on the other side of the stoma. If the ureter is very dilated, additional sutures may be needed on each side of the stoma. The sutures on one side of the stoma are tied and the polypropylene stent is removed. Then the remaining sutures are tied. The standard description of this technique recommends the use of 8-0 nylon swaged on a BV 130-5 taper needle (Ethicon Inc, Somerville, NJ) for the mucosal sutures. I prefer to use 8-0 polyglactin 910 swaged on a BV 130-4 taper needle (Ethicon Inc, Somerville, NJ) so that nonabsorbable suture material does not remain in the lumen of the urinary tract. After the mucosal sutures are completed, the bladder serosa and muscularis are apposed using simple interrupted sutures of 4-0 polydioxanone or polyglactin 910 to create a water-tight seal. The bladder is checked for leaks by injecting sterile saline into its lumen.

If there is tension on the anastomosis site between the ureter and the bladder, the kidney can be moved caudally (renal descensus) and the urinary bladder can be advanced cranially (psoas cystopexy).^7,9 The kidney is freed from its peritoneal and fascial attachments and moved to a more caudal and medial location taking care not to kink the renal vasculature. The renal capsule and a small amount of parenchyma is sutured to the body wall with 3 or 4 simple interrupted sutures of 4-0 nylon or polypropylene. To perform the cystopexy, the bladder is stretched cranially and the seromuscular layer of the dorsolateral bladder wall is sutured to the iliopsoas muscle with two or three simple interrupted nonabsorbable sutures.

Nephrostomy Tube Placement

Nephrostomy tube placement is indicated as an emergency procedure in cats with acute ureteral obstruction that are severely hyperkalemic and are poor candidates for a long surgical procedure. After instituting intravenous fluid therapy and attempting to lower the serum potassium concentration, the cat is anesthetized for nephrostomy tube placement. Although nephrostomy tubes can be placed percutaneously, it is recommended in cats they be placed via an open approach because feline kidneys are so mobile. A ventral midline celiotomy is performed to allow the kidney to be sutured to the body wall. Four sutures of 4-0 polydioxanone are placed from the greater curvature of the kidney to the dorsolateral body wall. The sutures are placed through the renal capsule and a small amount of renal parenchyma and through the transversus abdominus muscle and tied so that the kidney is secured to the body wall. The four sutures are placed to form a square (sutures are placed cranially, caudally, dorsally, and ventrally) so that the nephrostomy tube can be placed in the center of the square. A 5 French locking-loop pigtail nephrostomy catheter is preferred because it is less likely to become dislodged than a straight catheter.¹² A stab incision is made through the skin over the nephropexy site. Using ultrasound guidance, a 22-gauge intravenous catheter is inserted through the skin incision, body wall and greater curvature of the kidney into the renal pelvis at the site of the nephropexy. When urine backflows through the catheter, the stylette is removed. A urine sample is obtained from the renal pelvis for bacterial culture. At this point a pyelogram can be performed if desired. An angle-tipped hydrophilic 0.018-inch guidewire (Weasel Wire, Infiniti Medical LLC, Malibu, CA) is passed through the catheter and coiled in the renal pelvis. The catheter is removed over the wire. The pigtail nephrostomy catheter (5F Dawson-Meuller locking-loop pigtail catheter, Cook Medical, Bloomington, IN) is passed over the wire through the body wall and renal parenchyma and into the renal pelvis with the hollow cannula inside the pigtail catheter remaining secure to keep the catheter rigid during renal penetration. Once the tip of the pigtail catheter is confirmed to be in the renal pelvis, the cannula is immobilized as the catheter is advanced over the guidewire to form its loop. Once the loop of the pigtail is completely within the renal pelvis, the loop is locked in place by pulling on the string at the hub of the catheter. The string is secured and the cannula is removed from the catheter. The catheter is sutured securely to the skin and body wall with at least two friction sutures of 3-0 nylon. Each suture is tied tightly around the nephrostomy catheter being careful not to occlude the catheter lumen. The suture is then passed through the skin and body wall adjacent to the catheter. It is essential that the friction sutures are secured to the body wall and not just the skin because the mobility of the skin can cause dislodgment of the catheter. Alternatively, a Chinese finger trap suture may be used to secure the nephrostomy catheter. The nephrostomy catheter is attached to a sterile closed urine collection system. Following closure of the abdomen, a body bandage is applied to protect the nephrostomy tube.

If a locking-loop pigtail nephrostomy catheter is not available, a 16-gauge, 8-inch central venous catheter (Arrow International, Inc., Reading, PA) may be used for the nephrostomy tube. Additional side holes can be made near the tip of the catheter before catheter placement. A nephropexy is performed as previously described.

A small stab incision is made with a #11 blade through the skin at the site of the nephropexy. The intravenous catheter is passed through the stab incision and body wall and then through the greater curvature of the kidney and into the renal pelvis. When urine backflows through the catheter, the catheter is advanced off the stylette into the renal pelvis and the stylette is withdrawn. A guide wire is threaded through the catheter into the renal pelvis and the catheter is withdrawn over the wire. A dilator is passed over the wire and into the renal pelvis. The dilator is withdrawn and the single lumen catheter is threaded onto the guide wire. The catheter is advanced up the guide wire until the distal two centimeters of the catheter (including any side holes) are in the renal pelvis. The guidewire is withdrawn while holding the catheter in place. The catheter is secured in place as previously described.

Once the cat is stable medically, the nephrostomy tube can be used to perform antegrade pyelography to document persistence of the ureteral obstruction. If the ureter remains obstructed, definitive ureteral surgery can be performed. One disadvantage of performing a ureterotomy after a nephrostomy tube has been placed is that the decompressed ureter is less dilated so performing the ureterotomy is more challenging than it would have been during the acute obstruction.

Nephrostomy tubes can be useful in some cats following ureterotomy when there is concern that the ureterotomy site may leak or develop an obstruction due to severe postoperative inflammation. Antegrade pyelography is performed four to six days postoperatively to evaluate the patency and integrity of the ureter. If the ureter is patent and there is no evidence of leakage at the ureterotomy site, the nephrostomy tube is removed. Nephrostomy tubes have also been used to treat ureteral urine leakage that may occur as a complication in the postoperative period. Nephrostomy tubes can become dislodged or obstructed. In addition, they can allow urine leakage from the kidney into the peritoneal cavity or the subcutaneous tissues.^10,12 Nephrostomy tubes that are maintained for several days or weeks can be associated with chronic, antibiotic-resistant urinary tract infections. Because of their potential complications and the increased nursing care required, I prefer not to place nephrostomy tubes unless there is a high likelihood of urine leakage or urethral obstruction postoperatively.

Postoperative Care

Many cats with ureteroliths and nephroliths are anorectic, so a gastrostomy or esophagostomy tube is usually placed at the time of surgery for postoperative nutritional support. Intravenous fluids are administered for three to five days after surgery to promote diuresis. Many affected cats are anemic at the time of surgery and the anemia may worsen postoperatively. If the anemia is moderate to severe, whole blood or packed red cells should be administered. Serum creatinine concentration is measured daily for the first few days after ureterotomy. Although the serum creatinine in some cats decreases immediately after surgery, it is common for it to remain high or even increase during the first couple of days after surgery. This is most likely due to partial ureteral obstruction from swelling at the ureterotomy site. Intravenous fluid therapy is continued and after three to four days the creatinine usually begins to decrease. Fluid therapy is discontinued when the creatinine is within the reference range or has remained stable for several days. Postoperative antibiotic therapy is indicated only if a urinary tract infection is present.

Outcomes and Postoperative Complications

Prevention

Dietary therapy should be based upon quantitative analysis of the calculus. Most nephroliths and ureteroliths in cats are composed of calcium oxalate. There are commercially available diets for prevention of calcium oxalate uroliths. Ideally, a canned diet should be fed so that the cat consumes more water. The urine pH can be monitored. If it remains acidic in spite of the use of a non-acidifying diet, potassium citrate can be administered to alkalinize the urine. The cat should be monitored every three to six months for recurrence of calculi by abdominal radiographs, ultrasonography, urinalysis and urine culture. If the cat has chronic kidney disease, a CBC and serum biochemistries should also be evaluated.

Complications

Postoperative complications are common following surgical removal of ureteral calculi in cats. In a series of 88 cats that survived surgical removal of ureteroliths, 31% developed major postoperative complications and 18% of these cats died.¹⁰ Another report of 47 cats that underwent ureterotomy for urolith removal had a mortality rate of 21%.¹³ The most common complications following removal of ureteral calculi are urine leakage and persistent ureteral obstruction. Urine leakage is usually apparent within two to four days. The blood urea nitrogen and serum creatinine concentrations will increase and the cat may show abdominal pain. If uroabdomen does not resolve spontaneously and requires a second surgical procedure, the prognosis is guarded. In the previously cited case series, the mortality rate of cats that underwent a second surgical procedure because of uroabdomen was 27% (3/11).¹⁰ Three cats that developed uroabdomen were euthanized without additional surgery.¹⁰ Partial or complete obstruction of the ureter following ureterotomy may be transient due to swelling at the surgery site. If the cat is becoming progressively more azotemic two to four days following surgery, an excretory urogram or percutaneous antegrade pyelography should be performed to determine if there is urine leakage or ureteral obstruction. Stricture at the ureterotomy site could occur as a long-term complication but this is not detected often.¹⁴ Ureteral stricture can also be present at the time of initial surgery due to chronic ureterolithiasis and ureteral fibrosis. Approximately half of cats that recover from surgical removal of ureteroliths can be expected to have chronic kidney disease and maintain serum creatinine concentrations above the reference range.¹⁰ Recurrence of ureterolithiasis has been reported in 40% of cats in which serial abdominal imaging was performed after medical or surgical management.¹⁰ The second episode of ureterolithiasis occurred a median of 12.5 months (range 2 to 88 months) after the initial diagnosis.¹⁰

Editors Note: Minimally invasive therapy by interventional radiology has advantages when considering therapy for ureteral obstruction. Consultation with a specialist is recommended.

References

1. Lekcharoensuk C, Osborne CA, Lulich JP, et al: Trends in the frequency of calcium oxalate uroliths in the upper urinary tract of cats. J Am Anim Hosp Assoc 41:39, 2005.
2. Kyles AE, Hardie EM, Wooden BG, et al: Clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi: 163 cases (1984-2002). J Am Vet Med.Assoc 226:932, 2005.
3. Rivers BJ, Walter PA, Polzin DJ: Ultrasonographic-guided, percutaneous antegrade pyelography: technique and clinical application in the dog and cat. J Am Anim Hosp Assoc 33:61, 1997.
4. Adin CA, Herrgesell EJ, Nyland TG, et al: Antegrade pyelography for suspected ureteral obstruction in cats: 11 cases (1995-2001). J Am Vet Med Assoc 222:1576, 2003.
5. McClain HM, Barsanti JA, Bartges JW: Hypercalcemia and calcium oxalate urolithiasis in cats: a report of five cases. J Am Anim Hosp Assoc 35:297, 1999.
6. Berent AC: Ureteral obstructions in dogs and cats: a review of traditional and new interventional diagnostic and therapeutic options. J Vet Emerg Crit Care 21:86, 2011.
7. Kyles AE, Stone EA: Removal of nephroliths. In Bojrab MJ, Ellison GW, Slocum B, eds: Current Techniques in Small Animal Surgery, fourth ed. Baltimore: Williams & Wilkins, 1998, p 431.
8. Kyles AE, Stone EA, Gookin J, et al: Diagnosis and surgical management of obstructive ureteral calculi in cats: 11 cases (1993- 1996). J Am Vet Med Assoc 213:1150, 1998.
9. Mehl ML, Kyles AE, Pollard R, et al: Comparison of 3 techniques for ureteroneocystostomy in cats. Vet Surg 34:114, 2005.
10. Stone EA: Surgical management of urinary tract disease: ureteral calculi in cats and urinary bladder neoplasia in dogs. Compendium on Continuing Education for the Practicing Veterinarian 19:62, 1997.
11. Kyles AE, Hardie EM, Wooden BG, et al: Management and outcome of cats with ureteral calculi: 153 cases (1984-2002). J Am Vet Med Assoc 226:937, 2005.
12. Berent AC, Weisse CW, Todd KL, Bagley DH: Use of locking-loop pigtail nephrostomy catheters in dogs and cats: 20 cases (2004-2009). J Am Vet Med Assoc 241:348, 2012.
13. Roberts SF, Aronson LR, Brown DC: Postoperative mortality in cats after ureterolithotomy. Vet Surg 40:438, 2011.
14. Zaid MS, Berent AC, Weisse C, Caceres A: Feline ureteral strictures: 10 cases (2007-2009). J Vet Intern Med 25:222, 2011.
     

Introduction

Extracorporeal shock-wave lithotripsy (ESWL), in which high amplitude sound waves are generated outside the body and focused on a hard surface to create fissure and fragmentation, has been applied primarily to nephroliths and ureteroliths in dogs and people. In human medicine, adaptation of shockwave treatment revolutionized the treatment of urolithiasis in the 1980s,¹ and since that time, the addition of endosurgical and percutaneous techniques to ESWL have made open surgery of the urinary tract uncommon. As shock wave lithotripsy and laser lithotripsy have become more available in human medicine, a similar transformation is occurring in veterinary medicine; however, limited availability and cost of these procedures limits the number of patients who can be treated in this fashion. Additionally, variability in lithotriptors makes treatment protocols and responses difficult to compare; effectiveness will vary with machine type as well. Currently, the most common applications of ESWL include the treatment of nephroliths and ureteroliths in dogs, and treatment of ureteroliths in cats. In specific cases, ESWL can be applied to fragment urocystoliths as well.

Methods and Equipment Required

Application of shock-wave lithotripsy requires a source to generate shock waves, a method for focusing the shock waves (SW) to a solitary point, and a method for transmitting (or “coupling”) the SW to the patient. Shock waves are generated by electrohydraulic, electromagnetic, or piezoelectrical energy sources. With extracorporeal methods, the shock waves are generated outside the body, then reflected to converge on a target (the urolith) in the patient (Figure 29-15A,B). Like ultrasound waves, shock waves readily travel through fluid or soft tissue until they reach the “hard” acoustic surface of the urolith. Energy reflection, creation of tensile stresses along the surface of the stone, generation of cavitation bubbles, and dynamic fatigue lead to fragmentation with repeated shock waves.^2,3 Early lithotripsy treatments using the Dornier HM3 (Dornier, Marietta, GA), relied upon pulsatile sparks created by an electrohydraulic electrode and transmitted through a water bath medium (“wet” lithotripsy).^1,4,5 Newer lithotripters utilize other SW generators and “dry” methods, in which SW are coupled to the patient through a fluid filled cushion.^3,6-9 While these lithotriptors are easier to use and maintain, the efficacy of dry lithotriptors is lower than the “gold standard” water bath model, because of a smaller focal zone and in some cases, lower peak pressure. An advantage of this narrow focal zone is less damage to surrounding tissues; however, re-treatments are more common. The most recently produced lithotriptors are designed to increase portability and flexibility for various urologic procedures, as well as reduce cost of the equipment. Machines with mobile, handheld SW application sources may be useful for reaching uroliths in difficult locations and may allow for non-urologic applications (e.g. orthopedic) to be delivered by the same unit. However, these lithotriptors usually sacrifice efficiency and depth of penetration, which limits their effectiveness for nephroliths in larger human patients. While this would seem inconsequential in small animals, initial experience with the handheld units in dogs and cats suggests that efficiency is indeed sacrificed; a higher number of repetitive shocks and a higher retreatment rate are likely.¹⁰ The cost of equipment varies widely; reconditioned dry ESWL lithotripters require at least a several-hundred-thousand dollar investment.
 

In general, ESWL treatment includes general anesthesia of the animal, localization of the urolith in the lithotriptor’s focal zone, and application of sets of shock waves until sufficient fragmentation is observed on subsequent imaging. Shock-wave dose (power and number of shocks) and frequency varies depending on the patient and the machine settings. Usually, 1400-1500 SW are administered per kidney per treatment. Shock-waves are usually initiated at low power settings, then the power may be increased slowly to the effective level (usually 13 to 18 kV). Although this protocol was primarily created to improve patient comfort and procedure tolerance, it also affects urolith fragmentation by slowly creating small dust-like particles. Fluoroscopic or sonographic imaging is available for monitoring stone fragmentation. In-line sonographic visualization, such as that available with the Storz Modulith SL20 (Figure 29-16), can be very difficult in small animals and has not proven useful in our practice. Radiographic contrast media can be injected intravenously during treatment to enhance visualization of a ureterolith or radiolucent nephrolith; contrast nephropathy is possible, but rare.¹¹ Regardless of imaging capability, the degree of urolith fragmentation can be difficult to assess during treatment, since fragments may overly each other until they begin to move into the ureter.
 

Following lithotripsy treatment, a 2 to 4 day period of diuresis is continued to promote passage of stone fragments. Follow up radiographs and ultrasound are generally performed one or two days following treatment and every 3 to 4 weeks thereafter. Urolith passage may be rapid in some animals, or may take several months to completely clear from the urinary tract. Fragmentation has been considered complete in human beings when only clinically insignificant (< 2 mm) fragments remain visible.¹³ Based on veterinary experience, even smaller fragments are desired in small animal patients in order to facilitate passage of all debris along the ureter. Small residual fragments also can serve as a nidus for urolith recurrence in stone-forming individuals.^12,13

ESWL is contraindicated in animals with uncontrolled coagulopathy, hypertension, or other intra-abdominal disease such as chronic pancreatic or hepatic disease. Concurrent pyelonephritis or renal failure, while considered an indication for pursuing treatment of nephroliths, may increase the risk of SW induced renal injury in dogs and cats. I generally perform a more conservative lithotripsy regimen using less energy if measured glomerular filtration is subnormal, even if the animal is nonazotemic. Urinary tract infection should be managed and sterile urine obtained before performing ESWL. While small body size is not a contraindication, a greater percentage of the kidney is exposed to SW injury in patients or species with small kidneys.^14,15 The risk of damage to surrounding tissues, including lungs and bone, is also greater in very small animals.

Lithotripsy for Canine Nephroliths

If removal of nephroliths is indicated (progression in nephrolith growth, persistent urinary tract infection, presence of symptomatic or obstructive disease), lithotripsy is an option for treatment of the most common types of nephroliths in dogs (Table 29-1). Fragmentation of calcium oxalate nephroliths is reasonably effective in this species (Figure 29-17). In several reports, Adams has reported overall success in approximately 85% of dogs treated with the HM-3 lithotriptor.^4,11 We reported a similar overall response after our early experience with a Storz Modulith 20 dry lithotriptor,¹⁶ and have since found fragmentation of canine nephroliths highly variable. Treatment of nephroliths up to 2 or 3 cm in their largest dimension can be treated using this technology; however, smaller nephroliths (< 1.5 cm) are generally more amenable to treatment in our experience.

Struvite nephroliths also can be fragmented by ESWL permitting more rapid elimination or to hasten medical dissolution; we have treated one dog in which all radiographic evidence of a large nephrolith was gone in less than one month. However, medical dissolution of struvite nephroliths is preferred when feasible, particularly for very large stones. Urate, xanthine and cystine stones are more resistant to fragmentation. In 5 dogs with urate or xanthine stones, lithotripsy was effective in only 2.¹¹ For large or refractory uroliths, multiple treatments (separated by at least 4 weeks) may be considered. Ideally a ureteral stent is placed concurrently to facilitate fragment passage and prevent obstruction of the ureter. Transurethral, endoscopic ureteral stent placement may be feasible in some dogs using fluoroscopic guidance.¹⁷ The reported re-treatment rate for nephroliths varies with machines, ranging from 30%¹¹ to 50%.¹⁶

Bilateral nephroliths may be treated at the same time or staged, depending on the size of the nephrolith and renal function. Bilateral uroliths can be treated during the same anesthetic episode unless concern about individual renal function dictates staged treatments. Treatment of large stones may also be staged, due to high shock wave dose and anesthetic time needed to create fragmentation. Additionally, large fragments may be expected, leading to the increased likelihood or ureteral obstruction by stone fragmentation post-ESWL.¹¹
 

Potential Complications

Extracorporeal shock-wave lithotripsy, while considered safer than surgical approaches, is not without risk. Potential complications of lithotripsy for nephroliths include pain, the creation of obstructive ureteral fragments, damage to the kidney (parenchymal hemorrhage or subcapsular hematoma), or damage to other organs secondary to shock wave application. Adams (2013) estimates that 10% of ESWL treated dogs have transient ureteral obstruction. Stent placement or additional lithotripsy are indicated to alleviate persistent obstruction.^17a Transient hematuria, transient or progressive decrease in renal function, retroperitoneal fluid accumulation, ureterectasia, pain, diarrhea and ureteral obstruction by urolith fragments have been observed in dogs.^7,18 I routinely treat with analgesics for 24 hours post reatment, and extend the treatment if fragments are actively moving along the ureter, or if clinical signs of pain are observed. Acute pancreatitis has been described as a consequence of right kidney ESWL treatment in two small (< 5 kg) dogs, with fatal complications in one dog.¹⁹ Pancreatic injury may affect many ESWL treated dogs but clinical pancreatitis is seen in less than 2%.^17a Fatal arrhythmia, possibly secondary to shock waves, was recently described in one dog treated with the HM-3.¹¹ We have observed a transient ventricular arrhythmia in one cat during ESWL application. Residual fragments are common, and may provide a nidus for harboring infection or for formation of recurrent uroliths. Complications can be minimized by ensuring the health and suitability of the patient for anesthesia and shock wave treatment, ensuring appropriate shock wave dosage and application, shielding other organs from shock waves during treatment, ensuring adequate diuresis and monitoring post treatment, and providing prompt treatment of obstructive fragments.

Lithotripsy (ESWL) for Canine Ureteroliths

Ureteroliths can also be fragmented using ESWL. The method is similar to that for nephroliths, although their treatment can be more difficult for several reasons. Ureteroliths are more difficult to image and focus, are not in contact with as much fluid as stones in the renal pelvis, have less room for fragments to fall away, and may be imbedded in the ureteral wall.³ A higher shock wave dose may be required to sufficiently fragment ureteroliths. Using an aggressive treatment approach (mean 2600 SW at 14-19 kV) and a lithotripter with a small, high pressure focal zone, we have had very good success (> 90%) in fragmenting ureteroliths in dogs.^6,7 So far, only one ureterolith, lodged in the mid-ureter in a small dog (body weight < 3 kg), was insufficiently fragmented to pass after initial treatment. By comparison, retreatment rates for ureteroliths are approximately 50% using the HM3 lithotriptor.¹¹ Factors limiting successful fragmentation in human patients, that have led to an increase in ureteroscopic techniques, have included larger stone size (> 10 to 12 mm), distal (pelvic) location,^20,21 degree of obstruction and patient obesity.²⁰

The primary complication of ureterolith fragmentation is further ureteral obstruction. Fragmentation or movement of a ureterolith can create a more lodged stone, even if the ureterolith was nonobstructive initially. In our experience, ESWL treatment of ureteroliths can be more painful postoperatively than treatment of nephroliths. Dogs appear to tolerate passage of ureteral fragments well, presumably due to the size and distensibility of the canine ureter. Breakthrough pain is an uncommon finding in ESWL treated dogs, whereas pain can be excruciating during stone passage in people.

Limitations of ESWL for Feline Uroliths

ESWL treatment of uroliths in cats has been limited by disappointing early results. Adams observed significant renal trauma (renal hemorrhage and functional impairment) in a small number of healthy cat kidneys treated with the HM-3, as well as insufficient fragmentation of upper tract uroliths in 5 clinically affected cats.⁴ Using the HM-3 lithotriptor, Adams found that ureteroliths could be fragmented successfully in only 1 of 5 cats, and that fragmentation of nephroliths was incomplete. In addition, transient or permanent worsening of renal function occurred in several cats. Based on this experience, cat kidneys have been considered more sensitive to damage from ESWL.

Although promising results were obtained in a small group of healthy cats treated with a dry lithotriptor (no change in sonographic renal structure or function as assessed by renal scintigraphy)²² fragmentation of nephroliths or ureteroliths to the size needed to pass through the extremely small ureteral lumen still poses a considerable challenge.^10,11 Feline uroliths also are more difficult to fragment in vitro,²³ a finding that correlates with clinical experience. Using a research electrohydraulic lithotriptor that simulates the function of the Dornier HM-3, breakage of intact calcium oxalate uroliths retrieved from dogs and cats was evaluated using digital image size.²³ In this study from the Minnesota Urolith Center, significantly less breakage was observed in feline stones than in canine uroliths following the same SW dosage (100 SW at 20 kV).²³ Increased shock-wave dosage (especially shock-wave number, while still limiting power and frequency) may help minimize the size of fragments, but can only be effectively applied to one or two small stones during a treatment session. The number and size of nephroliths (or the finding of multiple, concurrent nephroliths, ureteroliths and cystoliths) makes lithotripsy impractical for stone removal in many cats. Renoprotective agents may help minimize renal injury during aggressive shock wave treatment. Logical protective measures also might include pre-treatment with mannitol or calcium channel blockers.

Lithotripsy for Feline Ureteroliths

Lithotripsy of ureteroliths in cats poses similar, but magnified, challenges when compared to those encountered in dogs. Imaging of very small ureteroliths in cats can be extremely difficult using the available fluoroscopic monitors (Figure 29-18A-C). Distal ureteroliths, in particular, can be obscured by pelvic structures, whereas other small ureteroliths can be difficult to place precisely in the focal zone. Movement of the ureterolith during ESWL appears much more common in cats as well, either with respiration or due to mobility of the ureter or urolith. Frequent repositioning and coordination with ventilation is imperative for effective fragmentation. We have reported progressively improving results in several feline ureteroliths treated with ESWL⁶ and have experienced an approximately 50% success rate (complete fragmentation and passage) after one or two treatments. Short term interim complications (retreatment, slow passage of fragments or debris) pose challenges; however most cats have had a favorable long term outcome. Unfortunately, further urinary tract compromise may occur in between treatments if the ureterolith remains obstructive. Surgical intervention is likely to alleviate obstruction more rapidly than lithotripsy in some cats, but is associated with significant morbidity.

Despite good fragmentation of a nephrolith, residual fragments still must be small enough to traverse the feline ureter (internal diameter < 0.4mm). Fluid and diuretic treatment to promote ureteral urine flow, or treatment with agents that may relax ureteral smooth muscle, are strategies that may improve the success of lithotripsy in cats. Based on experience with human beings, alpha antagonist and anti-inflammatory treatment may be the most promising adjunct treatments.²⁴ Amitriptyline also may relax urinary smooth muscle in cats.²⁵ Treated cats must be able to tolerate fluid diuresis, and should be screened for occult cardiac disease prior to treatment.

Although the primary risks of ESWL in cats have been viewed as damage to the kidney or worsening obstruction, other complications of ureteral treatments are possible. Ureteral rupture has been observed in one cat in our hospital. Pancreatic or bowel damage is also possible, given the size of the patient. Long-term effects on ureteral function or structure in small animals are currently unknown, but do not appear to be a major concern of ESWL in human patients.
 

Current Recommendations for Cats

At the current time, ESWL is most suited for treatment of a single (unilateral) obstructive ureterolith separated by some distance from the kidney. At this time, approximately one-half of cats with a single stone will have successful fragmentation of the stone (such that all fragments pass into the lower urinary tract) with one or two lithotripsy treatments. Obstructive nephroliths of small size (< 1 cm) also may be good candidates for ESWL, although the risk of renal injury increases with treatment of nephroliths. Owners of cats referred for lithotripsy should be prepared for multiple treatments, possible worsening of renal function, or progressive ureteral obstruction after ESWL (Table 29-2).¹⁰ Surgical intervention or dialysis support may be necessary if these complications are severe. For these reasons, surgery or ureteral stenting²⁶ may be a preferred option for metabolically unstable, patients with completely obstructive ureteroliths, where the immediate relief of obstruction is of primary concern. Potential modifications of lithotripsy protocols, including slow rate of energy delivery, lower power regiments, newer lithotriptors, and use of ureteral stents may minimize renal damage in cats.
 

Lithotripsy for Urocystoliths in Dogs or Cats

Extracorporeal shock wave lithotripsy has not been widely recommended for treatment of bladder stones. Free movement of uroliths within the bladder limits the effect of the carefully targeted, repetitive shock waves, and may result in failure of fragmentation, or larger fragments than desired. In some cases, however, urocystoliths can be fragmented fairly easily. Most commonly, urocystoliths are treated concurrently when nephroliths are treated.⁴ Extracorporeal lithotripsy can also be used to reduce the size of cystoliths for medical dissolution, removal by hydropropulsion, or prior to laser lithotripsy.¹¹ I have been pleased with the ability of the dry lithotriptor to fragment bladder stones for sufficient passage in several female dogs and one cat, but have avoided this treatment in male dogs due to the increased risk of urethral obstruction by small uroliths and stone fragments. Other clinicians have successfully applied the technique to small male dogs and removed the fragments by voiding urohydropropulsion.¹¹ A higher shock-wave dose may be required to create sufficiently small fragments; at this time it appears that urinary bladder tissue can tolerate this modification. For female dogs and cats, and male dogs large enough to undergo transurethral procedures, intracorporeal laser lithotripsy is preferred for optimal fragmentation of cystoliths.

Referral Considerations

The many new options for nonsurgical management of uroliths provide exciting opportunities for case management. Appropriate case selection, however, is critical to the success of the procedure and to client satisfaction. In addition to reviewing guidelines and information available regarding lithotripsy, clinicians should review the many summaries now available in textbooks and journals regarding general management of nephroliths and ureteroliths. Most referral centers providing lithotripsy treatment have prepared handouts or websites summarizing the indications, protocols and costs of therapy. Both referring clinicians and clients should be aware that access to a lithotriptor and availability of trained personnel may limit appointments and create delays in treatment. Facilities with in-house equipment are more likely to be able to accommodate emergency case referrals (ESWL for obstructive ureteroliths, laser lithotripsy for urethroliths). Clients should be prepared for 4 to 7 days of hospitalization for their animal and the possibility of multiple procedures and follow-up examinations over several months. Adequate local follow-up examinations, including high quality sonographic evaluation of the urinary tract, must be available. Repeat treatments, when indicated, are usually performed at 4 to 8 week intervals. Due to the intensity of pre-treatment and post-treatment patient handling, ESWL is not well suited for aggressive animals.

Appendix

Centers Providing Extracorporeal Shock Wave Lithotripsy

The Animal Medical Center
510 East 62nd Street
New York, NY 10065
Interventional Radiology and Endoscopy Contact: Phone: 212-838-8100 or info@amcny.org

Purdue University School of Veterinary Medicine Lynn Hall
625 Harrison Street
West Lafayette, IN 47906

Contact: Phone 765-494-1107 or PUSAH@purdue.edu ESWL, Laser

Tufts University Cummings School of Veterinary Medicine Foster Small Animal Hospital
200 Westboro Road
North Grafton, MA 01536

Contact: Phone: 508-839-5302 ESWL, Laser

References

1. Chaussy C, W B, E S: Extracorporeally induced destruction of kidney stones by shock waves. Lancet 2:1265, 1980.
2. Preminger G: Shock wave physics. American Journal of Kidney Disease 17:431-435, 1991.
3. Lingeman J, DA L, AP E: Surgical management of urinary lithithiasis, in Walsh P (ed): Campbell’s Urology, 8th edition. Philadelphia, WB Saunders, 2002, pp 3361-3452.
4. Adams LG, DF S: Electrohydraulic and extracorporeal shock-wave lithotripsy. Vet Clin North Am; Small Anim Pract 29:293-302, 1999.
5. Block G, Adams L: The use of extracorporeal shock-wave lithotripsy for treatment of spontaneous nephrolithiasis and ureterolithiasis in dogs. J Am Vet Med Assoc 208:531-536, 1996.
6. Lane I: Extracorporeal shock-wave lithotripsy for ureteroliths in dogs and cats, in 23rd American College of Veterinary Internal Medicine Forum, Baltimore, Md.
7. Lane I: Lithotripsy: an update on urologic applications in small animals. Vet Clin North Am; Small Anim Pract 34:1011-1025, 2004.
8. Bailey G, RL B: Dry extracorporeal shock wave lithotripsy for treatment of spontaneous nephrolithiasis and ureterolithiasis in dogs. J Am Vet Med Assoc 207:592-595, 1995.
9. Auge B, Preminger G: Update on shock wave lithotripsy technology. Current Opinion in Urology 12:287-290, 2002.
10. Lane I, Labato M, Adams LG: Lithotripsy, in JA A (ed): Consultations in Feline Internal Medicine, 5th ed. Philadelphia, Elsevier, 2006, pp 407-414.
11. Adams LG: Lithotripsy using shock waves and lasers, in 24th Annual ACVIM Forum, Louisville, KY, pp 439-441.
12. Tan Y, Wong M: How significant are clinically insignificant residual fragments following lithotripsy? Current Opinion in Urology 15:127-131, 2005.
13. Osman M, Alfano Y, Kamp S, et al: 5-year-follow-up of patients with clinically insignificant residual fragments after extracorporeal shockwave lithotripsy. European Urology 47:860-864, 2005.
14. Blomgren P, Connors B, Lingeman J, et al: Quantitation of shock wave lithotripsy-induced lesion in small and large pig kidneys. Anatomical Record 249:341, 1997.
15. Willis L, al e: Relationship between kidney size, renal injury and renal impairment induced by shock wave lithottripsy. J Am Soc Nephrol 10:1753, 1999.
16. Lane I: Dry extracorporeal shock-wave lithotripsy, in 21st American College of Veterinary Internal Medicine Forum, Charlotte, NC, June 2003.
17. Weisse CW, Berent AC. Interventional radiology in urinary diseases. In Bonagura J and Twedt D, Current Veterinary Therapy XIV, Saunders Elsevier 2009, pp 965-971.
18. 17a. Adams LG: Nephroliths and ureteroliths: a new stone age. N Zeal Vet J 61:212,2013.
19. Siems J, Adams, LG, et al.: Ultrasound findings in 14 dogs following extracorporeal shock-wave lithotripsy for treatment of nephrolithiasis [abstr]. In: in Proceedings of the American College of Veterinary Radiology Chicago, p 11.
20. Daugherty M, Adams LG, al e: Acute pancreatitis in two dogs associated with shock wave lithotripsy (abstr). Journal of Veterinary Internal Medicine 18:441, 2004.
21. Delakas D, Karyotis I, Daskalopoulos G, et al: Independent predictors of failure of shcokwave lithotripsy for ureteral stones employing a second-generation lithotripter. Journal of Endourology 16:201, 2003.
22. Shiroyanagi Y, Yagisawa T, Nanri M, et al: factors associated with failure of extracorporeal shock wave lithotripsy for ureteral stones using Dronier lithotriptor U/50. International Journal of Urology 9:304, 2002.
23. Gonzales A, Labato M, Solano M, et al: Evaluation of the safety of extracorporeal shock-wave lithotripsy in cats (abstr). Journal of Veterinary Internal Medicine, 2002.
24. Adams LG, JC W, JA M, et al: In vitro evaluation of canine and feline urolith fragility by shock wave lithotripsy (abstr). Journal of Veterinary Internal Medicine 17:406, 2003.
25. Porpiglia F, Ghignone G, C F, et al: Nifedipine versus tamsulosin for the management of lower ureteral stones. Journal of Urology 172:568, 2004.
26. Achar E, Achar R, Paiva T, et al: Amitriptyline eliminates calculi through urinary tract smooth muscle relaxation. Kidney International 64:1356, 2003.
27. Berent AC,Weisse CW,Todd KL, et al: Use of locking-loop pigtail nephrostomy catheters in dogs and cats: 20 cases (2004-2009). J Am Vet Med Assoc 241:348, 2012.
     

Introduction

Uroliths are a common cause of hematuria, stranguria, and dysuria in dogs.^1,2 Obstructive uroliths, if left untreated, may cause azotemia, recurrent urinary tract infections, loss of kidney function, or death.^1-3 Surgical removal is the traditional treatment for removal of recurrent stones or obstructive stones in veterinary medicine.^2,4-6 Surgery in the carefully selected patient is relatively quick, relieves obstruction, and decreases or reverses loss of glomerular function. However, surgery is invasive and complications, including damage to healthy functioning tissue, perioperative hemorrhage, urethral or ureteral stricture, intra-abdominal adhesions, and urolith recurrence are common.

Nephrotomy may cause a temporary decrease in renal function and nephron loss in those animals with preexisting renal disease. Recurrence of calculi formation, adhesions, and urine leakage may occur after cystotomy.^5,6 Leakage of urine from the kidney, ureter or bladder causes uroperitoneum and metabolic, fluid, electrolyte, and acid-base abnormalities. Incomplete removal of calculi especially from the bladder is not uncommon. Because of the small size and irregular contour of some uroliths, complete removal of all stones can be difficult.^7,8 Flushing the bladder and urethra is not a reliable method to ensure complete removal of all calculi; in one study, uroliths were incompletely removed in 1 of 7 dogs and 1 of 5 cats following cystotomy.⁹

Complications following urethrotomy include hemorrhage, urine leakage, and possible urethral stricture; and is indicated only if obstructive uroliths cannot be hydropropulsed retrograde into the bladder for dissolution or removal.^5,7,10 The urethrotomy site may be closed or left to heal by 2nd intention, in which case hemorrhage occurs for 7 to 10 days. Chronic stricture formation following urethrotomy increases the risk of blockage during voiding of calculi. Other potential complications include scarring of the incision site, tissue irritation, urethrocutaneous fistulae, and diverticula formation. Permanent urethrostomy may be necessary if stricture occurs. Complications of urethrostomy include hemorrhage, recurrent urinary tract infections, and inguinal and scrotal scalding.⁵

Lithotripsy

In human urology, surgical removal of uroliths has been largely replaced by lithotripsy.^1,11 Lithotripsy, the act of breaking or fragmenting stones, uses the generation of shock waves or laser energy to fragment uroliths. There are two forms of lithotripsy that use shock waves to fragment the stone; electrohydraulic shock-wave lithotripsy (EHL) and extracorporeal shock wave lithotripsy (ESWL). All shock waves, when focused, fragment urinary stones by erosion and shattering.^12,13

EHL uses the generation of sparks in a fluid medium to develop shock waves. The shock wave is generated at the tip of an insulated wire that is placed immediately adjacent to uroliths within the urinary tract. The shock wave passes through the body of a urolith and reflects back from its edge to pass back through the body of the stone. Many 1° and 2° shock waves are created, causing shearing forces that destroy the lattice of the urolith.^11,13 EHL has been used successfully in horses; successful ureteroscopic EHL was performed by perineal urethrostomy in a 3 yr. thoroughbred colt.¹⁴ In an 18-year old thoroughbred gelding, a ballistic shock wave lithotriptor was used to break up an 8 cm. bladder calculus and by flushing out the sand-like residue under epidural anesthesia.¹⁵

In ESWL, shock waves are generated outside the body and directed or focused toward the urolith. The stone is localized during lithotripsy with ultrasonographic or fluoroscopic guidance. ESWL is standard therapy for renal and upper urinary tract calculi in humans, with over 75 to 90% of stones resolved with lithotripsy.^12,13 Because of the relative immobility of the renal pelvis, ESWL is most applicable to renoliths that are relatively fixed as shock waves move through them. The relative mobility of the bladder and bladder stones makes ESWL less ideal for treatment of stones in the lower urinary tract.¹⁶ Nephroliths and ureteroliths have been successfully treated in dogs with 1st and 2nd generation lithotriptors.^1,17 Expense, purchase, upkeep, and availability of ESWL have limited its use in small animals.^13,17 (See ESWL by Dr. I. Lane).

Laser lithotripsy, an alternative to other forms of shock wave lithotripsy, effectively eliminates uroliths in humans, horses, ruminants, pigs, and dogs.^18-32 Laser-induced shock wave lithotripsy transforms light energy into acoustic energy (photoacoustic) or thermal (photothermal) energy, depending on pulse duration.²¹ The shock wave generated is large enough to fragment uroliths by photoacoustic or photothermal ablation.²¹ During lithotripsy, laser energy is transmitted and directed to the urolith surface through a small diameter flexible optical fiber that allows the operator to directly visualize the urolith under endoscopic guidance. The development of fiberoptic cables has greatly increased therapeutic applications of the laser, as fiberoptics allow the laser delivery beam to be brought in contact with the stone.²⁶ The small fiber size of a laser generally between 300 to 600 microns in diameter (0.3 to 0.6 mm), allows it to be passed through instrument channels in newer generation flexible and rigid endoscopes, and limits retropulsion. Fiberoptics allow the operator to safely, effectively, and accurately deliver laser energy and fragment a stone with little damage to surrounding tissue damage.^31-33 In humans, laser lithotripsy is the 2nd most preferred method for urinary calculi removal after shock wave lithotripsy.^18,34-35

A pulsed laser that can be delivered through fiberoptic cables is required. Pulsed laser energy is absorbed by water in the urolith, the resulting photothermal effect fragments the urolith, and fragments are actively flushed out with a flushing system attached to the endoscope’s biopsy port. Any remaining stone fragments are left to be passed normograde during urination.³¹ Because stones can be visualized endoscopically and the fiber is placed directly on the surface of the stone, the stone is consistently fragmented.^18,31 Laser lithotripsy is useful for patients at risk for hypertension or renal dysfunction, is non-invasive, protects renal function, and rapidly resolves clinical signs of obstruction.^26,36

Lasers used in Lithotripsy

Both the Holmium: Yttrium Aluminum Garnet (Ho:YAG) and pulsed dye lasers can effectively fragment biliary and urinary stones.^22,26,37 but the dye laser energy required for urolith fragmentation may damage the optical fibers and fragmentation efficiency is dependent on urolith composition and color.¹⁹ The pulsed dye laser has a wavelength of 504 nm, which is selectively absorbed by black or brown, the color of many uroliths. This is a disadvantage when treating “pale” uroliths such as cystine, because fragmentation may be ineffective for relatively colorless stones.³⁸ Pulsed dye laser lithotripsy is effective in fragmenting the most common uroliths of horses, calcium carbonate, and may be performed in standing horses with less surgical invasiveness and trauma to the urinary tract.²⁷ In male horses urethroliths are accessible at the distal urethra via a perineal urethrotomy or via a transurethroscopic approach. Transendoscopic pulsed dye laser lithotripsy was effective in the treatment of calcium carbonate urolithiasis in 2 adult geldings.²⁷ The principle disadvantages included cost of the procedure and the time delay required for use of the pulsed dye laser lithotriptor.

Success in fragmenting calcium carbonate uroliths in horses with Ho:YAG has been mixed; successful removal of calculi was reported in 5 horses with a combination of laser lithotripsy, lavage, basket snare removal, and digital manipulation.³⁹ In another report, the Ho:YAG failed to adequately fragment calculi, and pulsed dye lithotripsy or digital manipulation was necessary to remove the uroliths.⁴⁰

Initial experience in human urology with the Ho:YAG laser has demonstrated its safety and that no excess hemorrhage, renal deterioration or trauma occurs.²⁵ Reported stone-free rates are 67 to 84% for renal calculi, with complications rates of < 1%.²⁵ Ho:YAG lithotripsy is effective for ureteral and renal calculi in morbidly obese patients.²⁶ Additionally, the photothermal effects of the Ho:YAG laser use are minimal; lesions are consistently < 1 mm.^25,26

Advantages of the Ho:YAG laser for lithotripsy. The Ho:YAG laser is portable and rugged. The Ho:YAG laser precisely cuts with minimal damage to adjacent mucosal tissue. It offers fiber optic delivery, which is ideal for endoscopic use, and can treat tissue in a liquid environment such as the urinary tract. Protective eyewear is available for its infrared wavelength (2100 nm). Its laser wavelength is poorly absorbed in tissue, resulting in minimal damage to the adjacent urethral mucosa.^30-32 Its effect is independent of stone color.³⁸ Of all lasers, Ho:YAG produces the smallest fragments in all stone types. The reported efficacy of the Ho:YAG laser in fragmenting uroliths is 100% vs. 78 to 89%, for the pulsed dye laser.³⁸

Laser Lithotripsy in Veterinary Medicine

The Ho:YAG laser effectively fragments urinary stones independent of composition, water content, or size.^32,41 Pulsed Ho:YAG laser energy fragments canine uroliths in-vitro without optical fiber damage. In an initial in vitro study all stones were successfully fragmented in less than 30 seconds.³⁰ This and other studies have shown that that higher pulse frequencies (10 to 40 Hertz [Hz]) and lower pulse energies (≤ 1 joule[J]) were safer and more efficient for urolith fragmentation using Ho:YAG laser energy.^30,32,42

In a subsequent in vivo experimental study, laser lithotripsy with the Ho:YAG laser successfully fragmented obstructive uroliths in the urethra of male dogs.³¹ Mean time for adequate fragmentation was rapid, 166.7 seconds (range, 47 to 494.5 seconds). Minimal (< 30 mg) or no urolith material was evident within the urethra after lithotripsy. Urinary clinical signs related to lithotripsy resolved without further treatment in all dogs by day 5. Endoscopic evaluation of the urinary tract on day 10 revealed no mucosal lesions, stricture or narrowing of the urethra, or urolith remnants. No dog became obstructed during 30 days of observation.

Laser lithotripsy has been performed in male dogs with spontaneously occurring urolithiasis that could not be relieved with catheterization or urohydropropulsion (Figures 29-19 to 29-21). Stone burden ranged from one to seven per dog, and stone types were calcium oxalate or magnesium ammonium phosphate. Both urolith types in this group of dogs were successfully fragmented in less than 130 seconds in all dogs, and no complications from the procedure have been reported to date (Table 29-3). Differences in stone density or composition does not appear to affect the efficiency of laser fragmentation. No recurrence of clinical signs of obstructive urolithiasis or stricture formation has occurred in four dogs; one dog developed recurrent calcium oxalate cystoliths 25 months after lithotripsy which was treated via cystotomy.
 

Lithotripsy Technique for Urethral Calculi

All dogs with urinary calculi should have complete imaging (radiography and ultrasound) of the entire urinary tract, laboratory analyses including urinalysis and urine culture, and urine function and clotting studies if necessary prior to lithotripsy.

A 2.5 mm (7.5 French) (Karl Storz, Inc., Goleta, CA) or 2.8 mm (8.4 French) (Mitsubishi Endoscopy, Irvine, CA) flexible endoscope with an intraluminal channel is passed retrograde through the urethra to the level of the most distal urolith. A 320 um low-OH optical laser fiber (Sunrise Technologies, Fremont, CA) is passed through the operating channel until the aiming beam is visible extending from the tip of the endoscope. The fiber is directed onto the urolith surface and laser energy (sLase210 Ho:YAG laser, New Star Lasers, Auburn, CA) is applied in contact mode to the urolith surface until complete fragmentation occurs. Power settings are 5 Watt (W) power at 15 Hertz (Hz). Experience has shown that the total laser energy applied should be less than 1 J/pulse.³¹ Continuous flushing with normal saline (0.9% NaCl) solution delivered through the biopsy/irrigation port of the endoscope is performed during lithotripsy. This provides excellent visualization and allows normograde and retrograde flushing of the stones.

Fragmentation of the stone is considered complete when the fragments are easily flushed out through the urethra and the fragments are visually smaller than the urethral lumen at the level of the obstruction. Urethral obstruction occurs consistently at the level of the proximal or mid-os penis. The urethral mucosa is examined endoscopically before scope removal to determine that there is no immediately discernable gross damage to the mucosa.

In my clinical experience, all canine urolith types fragment consistently independent of composition, but continual readjustment and attention to the aiming beam position on the stone as it fragments is critical. Experience with use of the Ho:YAG laser is important to minimize potential complications including collateral tissue damage from reflected photoacoustic energy and risk of retropulsing a large fragment into the urinary bladder. Continual readjustment and attention to the aiming beam position on the stone as it fragments is critical. Continual flushing of the urethra or bladder to clear debris and fragments, and dilate the urethra during laser lithotripsy is helpful. Even when flushing is performed gently and overfill of the bladder is not permitted, iatrogenic bladder rupture can occur.⁴³

Lithotripsy Technique for Cystic Calculi

Despite advances in nutrition and antibiotic treatment, cystic calculi remain a common problem in dogs and cats.^7,8 Approximately 79 to 93% of all urinary calculi in dogs occur in the bladder.⁴⁴ Cystic calculi may cause recurrent urinary tract infections and obstruction. Traditionally, stones are removed by cystotomy, but surgical morbidity and cost of surgical removal are concerns especially when stones recur.⁵ There is not a widespread useful alternative to surgical removal of calculi in dogs.^4,5 Minimally invasive alternatives, such as laparoscopic cystotomy have been described, but are available on a limited basis.⁴⁵ ESWL has a high rate of residual stone fragments and is used primarily for ablation of ureteroliths or nephroliths because the relative mobility of the urinary bladder decreases its efficiency in fragmenting cystic calculi.¹³

Several recent studies have documented the efficacy of laser lithotripsy for the treatment of urethral and cystic calculi in dogs.^46,47,48 Lithotripsy using this technique is a minimally invasive procedure that appears to be a safe procedure with minimal complications. Depending upon the operator, anesthesia time can be longer than traditional surgical techniques such as cystotomy. Results of all three studies suggest that the use of laser lithotripsy is a safe and effective alternative to surgical removal of cystoliths and urethroliths in dogs (Table 29-3). At this time, laser lithotripsy is most available in academic or referral practices.

A brief description of cystic lithotripsy follows. A contrast urethrocystogram is performed prior to lithotripsy. In males, the dog is placed in dorsal recumbency and the prepuce and ventral abdomen are prepared aseptically. A 2.5 mm (7.5 Fr.) (Karl Storz, Inc., Goleta, CA) or 2.8 mm (8.4 Fr.) (Mitsubishi Endoscopy, Irvine, CA) flexible ureteroscope with an intraluminal channel is passed retrograde through the urethra to the bladder. In females, the dog is placed in dorsal recumbency with the hindquarters placed slightly beyond the edge of the table and elevated slightly. This allows the tail and hind limbs to remain out of the way and puts the dogs at a comfortable angle for the examiner.⁴⁹ A rigid 1.9 mm, 2.7 mm, or 4.0 mm cystoscope (Karl Storz Veterinary Endoscopy, Inc, Galeta, CA) is used for dogs < 10 kg, 10 to 20 kg, and 15 to 20 kg and above, respectively. The calculi are visualized and immobilized with an endoscopic basket (Securos endoscopic basket, Boston Scientific Inc., Boston MA) to grasp and immobilize each stone in preparation for fragmentation. Some stones do not need to be mobilized inside the basket; instead, lithotripsy is performed by immobilizing stones between the laser fiber and the bladder wall.

The remainder of the procedure is performed as for urethral lithotripsy. The entire bladder, with particular attention to the mucosa, should be examined endoscopically before scope removal to determine that there is no immediately discernable gross damage or large stone remnants. Random bladder biopsies may be performed after lithotripsy using a 3.5 mm endoscopic biopsy cup (apposing cup biopsy forceps, Karl Storz Veterinary Endoscopy, Goleta, CA).

Post Lithotripsy Recovery

Vital signs (temperature, pulse, respiration, and pain) are monitored routinely and patients generally are permitted water and food within 12 hours of the procedure. Dogs are monitored daily for gross hematuria, stranguria, and poilakiuria. Dogs frequently are poilakiuric initially. Mild to moderate hematuria and poilakiuria, if they occur, generally are self-limiting and resolve within 24 to 48 hours in affected dogs.³¹ Similar clinical signs routinely occur in humans after laser or extracorporeal shock wave lithotripsy.^12,13,36,50 Concurrent cystotomies to retrieve bladder uroliths that are not accessible with the laser result in clinical signs of hematuria and stranguria for several days postoperatively.⁵ Temporary urethral catheters in dogs are placed if moderate stranguria persists following lithotripsy. Catheterization is unnecessary in most cases, unless urethritis develops. In my experience, stranguria secondary to post-lithotripsy edema is more likely in dogs with chronic, multiple urethroliths.

Pronounced, prolonged stranguria or hematuria may indicate the presence of residual stones or more severe urethral mucosal damage. In those cases, additional imaging such as urethrography/cystography, endoscopic examination and retreatment may be necessary if the dog has evidence of obstructive urolithiasis (acute dysuria).

Remaining urolith fragments that are too small for further fragmentation or that retropulse proximally generally are voided normally within 24 hours.³¹ Small (< 30 mg) fragments should pass easily during urination after lithotripsy. Large (> 100 mg) fragments may result in reobstruction from incomplete fragmentation. A fragment that retropulses into the bladder during urethral lithotripsy or is not located during bladder lithotripsy may later move distally and lodge in the urethra at the level of the os penis. In human lithotripsy procedures, intraoperative contrast fluoroscopy is routinely performed to confirm that no large fragments remain.¹² Retropulsion increases as fiber diameter and pulse energy increases therefore small fibers should be used.⁵⁰ Alternatively, stones that are fragmented and photomechanically retropulsed into the urinary bladder may be removed laparoscopically.⁴⁵ This would avoid laparotomy, but requires an additional procedure.

In dogs with large fragments, repeat lithotripsy to treat recurrent obstruction is an option, but waiting for reobstruction to occur may not be satisfactory and could result in complications from obstructive urolithiasis. Regardless, dogs with clinical signs of reobstruction may have urethral endoscopy and repeat lithotripsy if necessary. The effect of multiple lithotripsy sessions on the lower urinary tract of dogs is unknown. Repeat lithotripsy has not been reported in the veterinary literature. Confirmation of complete fragmentation with post-lithotripsy contrast studies and observation of normal urination is advised.

Histologic mucosal changes following lithotripsy in humans and dogs include temporary erythema, erosion, hemorrhage, or ulceration.^30,31,38,51 Depending upon the location and microscopic character of the lesions, causes include damage from the urolith as it was placed or lodged into the urethra, mechanical damage from the endoscope or grasper as it is directed into the urethra, or damage associated with the fragmentation and flushing of stone fragments.³⁸ Long-term deleterious effects on the urethral mucosa from repeated laser lithotripsy are unlikely.⁵²

Lithotripsy for Treatment of Nephroliths

Surgical morbidity, effect on glomerular filtration rate, and cost of surgical removal of renoliths are important concerns in veterinary surgery.^4,5 To date, there is not a widespread alternative to nephrotomy or pyelolithotomy for removal of nephroliths in dogs. In human urology, surgical removal for renoliths and uteroliths has been superseded by minimally invasive procedures. Options for removal of stones in the renal pelvis include ESWL, percutaneous nephrolithotripsy (PCNL), intracorporeal or transureteral endoscopic retrieval, or laser lithotripsy.^{12,22,25,26,51}

ESWL is the most common technique for removal of kidney stones in humans, but has a higher rate of resistant residual stone fragments.^25,50 In addition, some stones located in the lower pole of the pelvis are not amenable to ESWL.⁴⁷ ESWL has been reported on a limited basis in veterinary medicine and is available at some referral practices.^1,13,17 Future advancements in ESWL therapy in veterinary medicine may occur as lithotriptors become more available.

PCNL In humans, allows a minimally invasive approach to the renal pelvis and renolith fragmentation with fluoroscopic or ultrasound guidance.⁵⁴ Renoliths larger than 3 cm in diameter, staghorn-shaped stones, calcium oxalate monohydrate stones, and cystine stones that are relatively resistant to ESWL are indications for PCNL.^26,38 Prior to lithotripsy, a percutaneous pyelogram may be performed to locate the exact stone position and size. The intrarenal collecting system is accessed through a percutaneous nephrostomy tract. In this procedure, a hollow needle is passed into the renal pelvis under fluoroscopic or ultrasonographic visualization. A flexible guide wire is then passed through the hollow needle and manipulated through the ureter. The nephrostomy tract is formed by dilating the skin abdominal wall muscles, and renal tissues using progressively larger plastic dilators or a balloon catheter. After the tract has been adequately dilated, a hollow plastic sheath is placed into the tract into the renal pelvis. A rigid or flexible endoscope is passed into the pelvis and/or proximal ureter. Stones are retrieved with an endoscopic basket if very small. If they are larger, a Ho:YAG laser fiber is placed into the central operating channel of the endoscope and lithotripsy is performed. Laser energy delivered to the surface of the stone creates photothermal energy that reduces the stone to tiny fragments, the majority of which are washed out with the irrigant.^21,51 The cutaneous tract is left to heal by second intention.

Initial experience in humans with the Ho:YAG laser has demonstrated its safety. There is no evidence of decreased renal function after Ho:YAG lithotripsy.²⁵ In a study of 25 pediatric patients, only one had significant decrease in glomerular filtration rate (GFR) following Ho:YAG PCNL.²² Additionally, only one of 18 patients in a retrospective study had decreased GFR > 20% (the threshold for significant decrease). There was no correlation between GFR and stone size, stone location, or energy.⁴⁷

Reported stone free rates are 67 to 84% for renal calculi, with complications rates of < 1%.²⁵ Ho:YAG lithotripsy is effective for ureteral and renal calculi in morbidly obese patients who are not candidates for ESWL. Additionally, the photothermal effects of the Ho: YAG laser are minimal; lesions were consistently less than one mm.²⁵ In the future, laser lithotripsy with PCNL may offer a non-invasive, cost-effective, rapid treatment option for dogs with nephroliths. Studies to evaluate and modify the technique for use in small animals are being performed.

Conclusion

Laser lithotripsy is a non-invasive, cost-effective, rapid treatment option for dogs with urinary calculi in the bladder and/or urethra.

This is especially important for breeds (or individual dogs) that are predisposed to recurrent urolith formation. Techniques for laser fragmentation of obstructive uroliths in the urethra and bladder have been established. Further advancements in lithotripsy in veterinary patients may obviate the need for traditional surgery.

Until the complex and multifactorial causes of stone formation in dogs are elucidated and stone formation is preventable, the further development of minimally invasive treatment protocols that prevent the need for multiple surgical procedures has many advantages. Laser lithotripsy appears to have applications for treatment of urolithiasis, a common and potentially dangerous health problem in dogs. In particular, successful laser lithotripsy may reduce or prevent associated problems that affect animal urinary health such as urinary tract infections, acute dysuric obstruction, and hydroureter/hydronephrosis. Potential disadvantages of laser lithotripsy include patient and operator safety issues, cost, laser maintenance, and the training and experience required for successful stone fragmentation.

References

1. Block G, Adams LG, Widmer WR, et al: Use of extracorporeal shock wave lithotripsy for treatment of nephrolithiasis and ureterolithiasis in five dogs. J Am Vet Med Assoc 208:531, 1996.
2. Osborne CA, Lulich JP, Unger LK, et al: Canine and feline urolithiasis: relationship of etiopathogenesis with treatment and prevention In: Bojrab MJ, ed.: Disease Mechanisms in Small Animal Surgery. Philadelphia: Lea & Febinger, 1993, p 464.
3. Lulich JP, Osborne CA: Canine calcium oxalate uroliths In: Bonagura JD, Kirk RW, eds.: Current Veterinary Therapy XII, Philadelphia: Saunders, 1995, p 992.
4. Rawlings CA, Bjorling DE, Christie BA: Nephrolithiasis In Slatter D, ed.: Textbook of Small Animal Surgery, 2nd ed. Philadelphia: WB Saunders, 2003, p 1610.
5. Kyles AE, Aronsohn M, Stone EA: Complications of urogenital surgery In: Lipowitz AJ, Caywood DD, Newton CD, et al, eds.: Complications in Small Animal Surgery, Baltimore: Lea and Febiger, 1996, p 455.
6. Collins RL, Birchard SJ, Chew DJ, et al: Surgical treatment of urate calculi in Dalmatians: 38 cases (1980-1995) J Am Vet Med Assoc 1998; 213:833-837.
7. Lulich JP, Osborne CA, et al: Nonsurgical removal of uroliths in dogs and cats by voiding urohydropropulsion. J Am Vet Med Assoc 203:660, 1993.
8. Lulich JP, Osborne CA, et al. Management of canine calcium oxalate urolith recurrence. Compend Contin Educ Pract Vet 1998; 20: 178-189.
9. Lulich JP, Osborne CA, Polzin DP, et al: Incomplete removal of canine and feline urocystoliths by cystotomy. J Vet Intern Med 7:221, 1993.
10. Osborne CA, Lulich JP: Canine retrograde urohydropropulsion: lessons from 25 years of experience. Vet Clin North Am: Small Anim Pract 29:267, 1999.
11. Auge BK, Preminger GM: Update on shock wave lithotripsy technology. Cur Opin Urol 12:287, 2002.
12. Stoller ML: Extracorporeal shock wave lithotripsy: intraoperative considerations. In: Tanagho EA, McAninch JW, eds.: Smith’s General Urology 14th ed. Norwalk:Appleton and Lange, 1995, p 307 .
13. Adams LG, Senior DF: Electrohydraulic and extracorporeal shockwave lithotripsy. Vet Clin North Am Small Anim Pract 29:293, 1999.
14. Rodger LD, Carlson GP, Moran ME, et al: Resolution of a left ureteral stone using electrohydraulic lithotripsy in a thoroughbred colt. J Vet Intern Med. 9:280, 1995.
15. Koenig J, Hurtig M, Pearce S, et al: Ballistic shock wave lithotripsy in an 18-year old thoroughbred gelding. Can Vet J 40:185, 1999.
16. Jou YC, Shen JH, Cheng MC, et al: Percutaneous nephrolithotomy with Ho:YAG laser and fiber guider- report of 349 cases. Urol 65:454, 2005.
17. Bailey G, Burk RL: Dry extracorporeal shock wave lithotripsy for treatment of ureterolithiasis and nephrolithiasis in a dog. J Am Vet Med Assoc 207:592, 1995.
18. Hofmann R32, Hartung R,33 Schmidt-Koiber H, et al: First clinical experience with a Q-switched neodymium:YAG laser for urinary calculi. J Urol 141:275, 1988.
19. Dretler SP, Watson G, Parrish JA, et al: Pulsed dye laser fragmentation of ureteral calculi: initial clinical experience. J Urol 137:386-389, 1987.
20. Watson G, Murray S, Dretler P, et al: The pulsed dye laser for fragmenting urinary calculi. J Urol 138:195, 1987.
21. Chan KF, Vassar GJ, Pfefer TJ, et al: Ho:YAG laser lithotripsy: a dominant photothermal ablative mechanism with chemical decomposition for urinary calculi. Lasers Surg Med 25:22, 1999.
22. Mor Y, Elmasry YE, Kellett MJ, et al: The role of percutaneous nephrolithotomy in the management of pediatric renal calculi. Urol 158:1319, 1997.
23. Lahme S, Bichler KH, Strohmaier WL, et al: Minimally invasive PCNL in patients with renal pelvic and calyceal stones. Eur Urol 20:619, 2001.
24. Zorcher T, Hochberger J, Schrott KM, et al: In vitro study concerning the efficiency of the frequency-doubled double-pulse Neodynium:YAG laser (FREDDY) for lithotripsy of calculi in the urinary tract. Lasers Surg Med 25:38, 1999.
25. Teichman JMH. Laser lithotripsy. Curr Opin Urol 12:305, 2002.
26. Higashihara E, Horie S, Takeuchi T, et al: Laser ureterolithotripsy with combined rigid and flexible ureteroscopy. J Urol 143:273, 1990.
27. Howard RD, Pleasant RS, May KA:Pulsed dye laser lithotripsy for treatment of urolithiasis in two geldings. J Am Vet Med Assoc 212:1600, 1998.
28. Halland, SK, House JK, George LW: Urethroscopy and laser lithotripsy for the diagnosis and treatment of obstructive urolithiasis in goats and pot-bellied pigs. J Am Vet Med Assoc 220:1831, 2002.
29. Streeter RN, Washburn KE, Higbee RG, et al: Laser lithotripsy of a urethral calculus via ischial urethrotomy in a steer. J Am Vet Med Assoc 219: 640, 2001.
30. Wynn VM, Davidson EB, Higbee RG, et al: In vitro assessment of Ho:YAG laser lithotripsy for the treatment of canine urolithiasis. Proc SPIE, Progress in Biomedical Optics and Imaging 4609:241, 2002.
31. Davidson EB, Ritchey JW, Higbee RD, et al: Laser lithotripsy for treatment of canine uroliths. Vet Surg 32:51, 2004.
32. Wynn VM, Davidson EB, Higbee RG, et al: In vitro effects of pulsed Holmium laser energy on canine uroliths and porcine cadaveric urethras. Lasers Surg Med 33:243, 2003.
33. Grasso M, Bagley D: Small diameter, actively deflectable, flexible utereropyeloscopy. J Urol 160:1648, 1998.
34. Psihramis KE, Buckspan MB: Laser lithotripsy in the treatment of ureteral calculi. Can Med Assoc J 142:833, 1990.
35. Bagley DH: Expanding role of ureteroscopy and laser lithotripsy for treatment of proximal ureteral and intrarenal calculi. Curr Opin Urol 12:270, 2002.
36. Bataille P, Pruna A, Cardon G, et al: Renal and hypertensive complications of extracorporeal lithotripsy. Presse Med. 29:34, 2000.
37. Kopecky KK, Hawes RH, Bogan ML, et al: Percutaneous pulsed-dye laser lithotripsy of gallbladder stones in swine. Investig Radiol 25: 627, 1990.
38. Matsuoka K, Iida S, Inoue M, et al: Endoscopic lithotripsy with the olmium:YAG laser. Lasers Surg Med 25:389, 1999.
39. Judy CE, Galuppo LD: Endoscopic assisted disruption of urinary calculi using a Holmium:YAG laser in standing horses. Vet Surg 31:245, 2002.
40. May KA, Pleasant RS, Howard RD, et al: Failure of holmium: yttrium-aluminum-garnet laser lithotripsy in two horses with calculi in the urinary bladder. J Am Vet Med Assoc 219:957, 2001.
41. Woods JP, Bartels KE, Stair EL, et al: Laser-induced shock wave lithotripsy of canine urocystoliths and nephroliths. Proc SPIE Progress in Biomedical Optics 2970: 227, 1997.
42. Spore SS, Teichman MH, Corbin NS, et al: Holmium:YAG lithotripsy: optimal power settings. J Endourol 13:559, 1999.
43. McCarthy TC, McDermaid SL: Cystoscopy. Vet Clin North Am: Small Anim Pract 20:1315, 1990.
44. Ling GV, Franti CE, Ruby AL, et al: Urolithiasis in dogs I: mineral prevalence and interrelations of mineral composition, age, and sex. Am J Vet Res 49: 624, 1998.
45. Rawlings CA, Mahaffey MB, Barsanti JA, et al: Use of laparoscopic-assisted cystoscopy for removal of urinary calculi in dogs. J Am Vet Med Assoc 222:759, 2003.
46. Adams LG, Berent AC, Moore GE, et al: Use of laser lithotripsy for fragmentation of uroliths in dogs: 73 cases (2005-2006). J Am Vet Med Assoc 232: 1680,2008.
47. Lulich JP, Osborne CA, Albasan H, et al: Efficacy and safety of laser lithotripsy in fragmentation of urocystoliths and urethroliths for removal in dogs. J Am Vet Med Assoc 234: 1279, 2009.
48. Bevan JM, Lulich JP, Albasan H, et al: Comparison of laser lithotripsy and cystotomy for the management of dogs with urolithiasis. J Am Vet Med Assoc 234:1286, 2009.
49. Senior DF, Sundstrom DA: Cystoscopy in female dogs. Compend Contin Educ Small Anim Pract 10:890, 1988.
50. Lee H, Ryan RT, Teichman JM, et al: Stone retropulsion during holmium:YAG lithotripsy. J Urol 169:881, 2003.
51. Vorreuther R, Corleis R, Klotz T, et al: Impact of shock wave pattern and cavitation bubble size on tissue damage during ureteroscopic electrohydraulic lithotripsy. J Urol 153:849, 1995.
52. Kostolich M, Bartels KE, Schafer S, et al: Ho:YAG laser ablation of alimentary tract mucosa. In: Proceedings of Lasers in Orthopedic, Dental, and Veterinary Medicine, Los Angeles, pp. 74, 1993.
53. Sundaram CP, Slatzman B: Extracorporeal shock wave lithotripsy: a comprehensive review. Comp Ther 24:332, 1998.
54. Irby PB, Schawartz BF, Stoller ML: Percutaneous access techniques in renal surgery. Tech Urol 5:29, 1999.
55. Fry TR. Laser safety Vet Clinic North Am Small Anim Pract 32:535, 2002.
     

Introduction

Clinical renal transplantation in cats was performed successfully in 1984 by Dr. Clare Gregory and Dr. Ira Gourley at the University of California-Davis, School of Veterinary Medicine. The ability to successfully perform renal transplantation as treatment for renal failure in companion animals was due to a number of factors including the development of microsurgical techniques and the availability of microsurgical equipment in veterinary practice, the ability to use an allograft from an unrelated donor and the administration of cyclosporine for immunosuppressive therapy in the dog and cat.^1-3

Results published in 1992 evaluating the first 23 cases of feline renal transplantation, supported transplantation as a treatment option for cats in end stage renal failure. In that study, 70% of the cats were discharged from the transplant facility and the mean survival period was 12 months for all cats with the longest surviving for 31 months.⁴ In 1996, a retrospective study evaluating 66 cases of feline renal transplantation (including the 23 cases that had been previously described) was published.⁵ In that study, although the percentage of cats surviving to discharge was similar to the first report during the 9 year study period, there was an improvement in perioperative survival. Perioperative survival rate improved from 64% in the first 33 cats to 79% for the last 33 cats.⁵ It is estimated that over 400 feline renal transplants have been performed since the procedure was first introduced in 1984. Although a retrospective study describing all cases that have been performed to date is not available, recent information from veterinary surgical centers active in tranplantation suggests that survival times are continuing to improve (Table 29-4). Improved survival may be related to more stringent case selection, as well as the clinician’s ability to better recognize and treat complications both in the immediate postoperative period and long term. Cats are the predominant species to undergo transplantation and will be the focus of this chapter, however information will also be presented on canine transplantation since it is becoming more common at selected university hospitals.
 

Client Education

It is important for clients to realize that renal transplantation is a treatment option for animals in chronic renal failure, but is not a cure. Medical therapy including subcutaneous fluid therapy, low protein diets, phosphate binders, hormonal therapy including Erythropoietin and Darbopoietin, gastrointestinal protectants, and antihypertensive medication can often be discontinued following surgery however the pet will still need immunosuppressive therapy for life. Selection criteria for transplantation are rigorous and the owner needs to understand the risks of the procedure and that their cat may be turned down as a potential candidate if the cat fails any aspect of the medical screening process or if the cat has a fractious temperament. The cost of renal transplantation is high and additional veterinary visits postoperatively for monitoring of renal function and determining serum levels of cyclosporine are required. It is necessary for the owner to identify a veterinary hospital that can provide 24 hour care and a veterinarian who is willing to care for a renal transplant recipient. Finally, a critical aspect of any transplant program is donor adoption. The client must be willing to provide a lifelong home for the donor animal regardless of the outcome of the transplant procedure.

Evaluation of a Potential Recipient

Thorough screening, which is often performed by the referring veterinarian working with the transplant surgeon, is essential for a potential feline renal transplant recipient to decrease the incidence of morbidity and mortality that can occur following the surgical procedure. Although the ideal time to perform transplantation is not known, experienced clinicians suggest that the best candidate for renal transplantation is a cat in early decompensated renal failure.^6,7 Indications of decompensation include continued weight loss and worsening of anemia and azotemia in the face of medical management. Although attempts to alter the physical deterioration of animals with chronic renal failure have been reported to be unsuccessful, the placement of either an esophagostomy tube or percutaneous endoscopic gastrostomy (PEG) tube has been used successfully for up to 2 years for the medical management of some potential renal transplant candidates^6,7 (Personal communication, Mathews, KG). It is noted that the degree of azotemia, anemia, urine specific gravity and age, do not determine a suitable patient for transplantation. In one report, cats greater than 10 yrs of age had an increase in mortality, particularly during the first 6 months following surgery.⁸ To date, the oldest cat that has had successful transplantation at our hospital was 18 years of age.

Both physical and biochemical parameters should be carefully evaluated to determine if a cat is suitable for transplantation. Current evaluation in our hospital includes laboratory testing (complete blood count/chemistry/blood type and crossmatch/ thyroid evaluation), evaluation of the urinary tract (urinalysis, urine culture, urine protein:Cr ratio, abdominal radiographs, abdominal ultrasound), evaluation for cardiovascular disease (thoracic radiography, blood pressure electrocardiography, echocardiography, and infectious disease screening (FeLV/FIV, Toxoplasma titer, IgG and IgM) (Table 29-5).
 

Evaluation of the Urinary Tract

Evaluation of the urinary tract to rule out underlying infection or neoplastic disease is essential prior to transplantation. Based on biopsy reports from cats that have been transplanted, the most common diagnosis of renal disease is chronic tubulointerstitial nephritis. Other diseases successfully treated by transplantation include polycystic kidney disease, membranous glomerulonephropathy, calcium oxalate urolithiasis and ethylene glycol toxicity.⁶ If on abdominal ultrasound, renomegaly is identified and the cause is not polycystic kidneys or perinephric pseudocysts, then a fine needle aspirate or a biopsy is recommended to rule out Feline Infectious Peritonitis (FIP) or neoplasia. Animals diagnosed with a urinary tract infection should be treated with the appropriate antibiotic therapy based on culture and sensitivity prior to presentation. In patients with recurrent urinary tract infections or those that have recently been treated, but at the time of presentation have a negative urine culture, a Cyclosporine (CsA; Neoral, Sandoz Pharmaceuticals) challenge is indicated. The patient is administered Cyclosporine for approximately two weeks at the recommended dose for transplantation immunosupression. The urine is evaluated for the presence of an infection on at least 2 occasions; after therapeutic CsA blood levels have been obtained and at the end of the 2 week period. Although negative urine culture results will not guarantee that a patient will remain infection free after transplantation and chronic immunosupression, it can eliminate some cats with occult infections. Alternatively, all potential transplant candidates can be treated with CsA for 2 weeks prior to surgery to attempt to identify occult infection prior to transplantation.⁷

The incidence of cats with calcium oxalate (CaOx) urolithiasis and concurrent renal failure and subsequent presentation of the cat for renal transplantation, has been increasing. In a recent retrospective study, renal transplantation was a successful treatment option for cats whose underlying cause of renal failure was associated with CaOx urolithiasis.⁹ No difference in long term outcome was found between a group of 13 stone formers and a control group of 49 cats whose underlying cause of renal failure was not related to stone disease. If hydronephrosis is present on abdominal ultrasound during the recipient screening process, a pyelocentesis and urine culture is recommended prior to transplantation to identify patients that may be harboring an infection. The author has identified five cats with obstructive CaOx urolithiasis that have had a negative urine culture from urine collected from the urinary bladder and a positive urine culture from urine collected by pyelocentesis (L.R. Aronson unpublished data 2005). Allograft rejection as well as an increase in morbidity and mortality can occur in an immunosupressed patient harboring an infection.

Cardiovascular Disease

Many cats presented for transplantation have systolic murmurs identified on physical examination. These murmurs may be secondary to the anemia of chronic renal failure and not represent significant heart disease.⁶ Historically, because of complications associated with transplanting cats with hypertrophic cardiomyopathy, cats with underlying cardiac disease were not accepted into the program. In a recent study performed at the University of California-Davis evaluating cardiac abnormalities in 84 potential transplant recipients, only 22% were found to have a normal heart on echocardiographic examination. The most common abnormalities identified included both papillary muscle and septal muscle hypertrophy and it was suggested that these changes may be related to chronic uremia, hypertension, age or early changes of hypertrophic cardiomyopathy.¹⁰ We have identified patients with similar changes on echocardiography that were unable to tolerate fluid therapy prior to transplantation. Four patients developed varying degrees of pulmonary edema and pleural and pericardial effusion. Following transplantation, fluid therapy was reinitiated without complication. In 2 cats, echocardiographic evaluation performed within 3 months following surgery revealed resolution of echocardiographic abnormalities. Potential candidates with diffuse hypertrophic cardiomyopathy or those with congestive heart failure are declined as candidates for renal transplantation in our hospital. In cats with less severe cardiac disease, a decision is made on a case to case basis.

Infectious Disease

If a cat has an active FIV infection or is FeLV positive, they are declined as candidates for transplantation. All potential transplant donors and recipients currently undergo serologic testing (IgG and IgM) for Toxoplasmosis. Toxoplasma gondii can cause significant morbidity and mortality in both human and veterinary immunocompromised patients. Most human transplant patients will display clinical signs within the first 3 months following surgery since this is the period of maximum immunosupression.¹¹ In a report describing 3 cats and 1 dog, disseminated toxoplasmosis occurred within 3 weeks to 6 months following transplantation.¹² As a matter of policy at our facility, we do not use seropositive donors for seronegative recipients, but we have successfully used a seropositive donor for a seropositive recipient. Seropositive recipients are placed on lifelong prophylactic Clindamycin (25 mg PO q12h) which is started in conjunction with immunosupression. Tribrissen has also been used in cats that did not tolerate Clindamycin. To date, 10 recipients with a positive IgG and/ or a positive IgM titer have been placed on prophylactic Clindamycin therapy. Two cats are currently alive 105 and 545 days following transplantation. Eight cats have died a median of 379 days following transplantation. Cause of death included, lymphosarcoma (3 cats), presumed antibiotic toxicity (1 cat), cardiomyopathy (1 cat), accidental avulsion of the allograft (1 cat), chronic pyelonephritis (1 cat) and allograft failure (1 cat). None of the cats died from an active Toxoplasma gondii infection (L.R. Aronson unpublished data 2005).

Although we have become more selective in case selection in recent years, with the availability of hemodialysis and the increasing experience of clinicians who manage these cases we have “pushed the envelope” by performing transplants on cases that may be considered questionable recipients. Definitive findings that preclude renal transplantation include cats with neoplastic disease, severe cardiac disease, FeLV positive status, active FIV infection, recurrent or existing urinary tract infection that fails medical therapy and/or a CsA challenge, uncontrolled hyperthyroidism and a fractious temperament. (Table 29-6). Although objective information associated with survival has been identified with regard to some aspects of the screening process in recipients, some clinical uncertainties continue to pose challenges including animals with inflammatory bowel disease, diabetes mellitus, and those cats with echocardiographic abnormalities that are not able to receive fluid therapy without causing fluid overload (See Table 29-6).
 

Evaluation of a Potential Donor

Cats selected as kidney donors are in excellent health and are typically between 1 to 3 years of age. Standard evaluation includes a serum chemistry profile, complete blood count, urinalysis and culture, FeLV and FIV testing and a Toxoplasmosis titer (IgG and IgM). The feline kidney donor must also be bloodcross match compatible to the recipient and of a similar size. Additionally, CT angiography is performed on all of the potential donors to evaluate the renal vasculature as well as evaluate the renal parenchyma for any abnormalities (Table 29-6).¹³ This screening technique has allowed us to identify potential donors unsuitable for donation including those with renal infarcts as well as the presence of multiple arteries. A suitable home is found for any donor that fails the screening process. In a study evaluating the long term effects of performing a unilateral nephrectomy in a healthy cat, 16 donors were followed between 24 and 67 months postoperatively.¹⁴ Fifteen of the 16 cats were clinically normal and serum creatinine concentrations for these cats remained within the reference range. One cat was diagnosed with chronic renal insufficiency 52 months following surgery. Although renal donation does not appear to affect normal life expectancy, long term monitoring is recommended in these animals.

Preoperative Recipient Treatment

Preoperative care for the recipient varies depending on the stability of the animal. At some centers, hemodialysis is performed prior to surgery in cats with severe azotemia (BUN > 100 mg/ dL, Cr > 8mg/dL).⁸ In cases that do not require hemodialysis, the recipient is typically placed on intravenous fluid therapy of a balanced electrolyte solution at 1.5 to 2 times the daily maintenance requirements. In some cases, underlying cardiac disease may preclude this rate of fluid administration because of the risk of development of pulmonary edema and pleural effusion. Additionally, the calcium channel blocker amlodipine (Norvasc, Pfizer labs, 0.625 mg/cat PO q24h) may be indicated prior to surgery if the cat is hypertensive. Anemia is typically corrected with either whole blood transfusions or packed red cells with the goal of obtaining an endpoint packed cell volume of 30% prior to surgery. If the cat is stable on admission with respect to anemia, blood transfusions are administered at the time of surgery. The first unit that is administered is a unit previously collected from the cross-match compatible donor cat. It is important to note that some cats in chronic renal failure are not transfusable because of incompatabilities despite the fact that the cats are of the same blood type and have had no known exposure to blood products. If the patient is traveling a great distance to the transplant hospital, blood crossmatching should be performed prior to admission. A blood sample can be sent to the transplant hospital for cross-matching in order to identify a compatible kidney donor as well as identify 2 to 3 potential blood donors. Hormonal therapy including Erythropoietin or Darbopoietin can be administered if a delay is expected and can greatly reduce the need for blood products at the time of surgery. Although uncommon, the owner should be cautioned regarding the possibility of the development of antibodies to these drugs which can result in significant morbidity and potentially mortality in the postoperative period. If deemed necessary, phosphate binders and gastrointestinal protectants can be given and if the cat is anorectic, a nasogastric, esophagostomy or PEG tube may be placed prior to surgery to administer nutritional support.

Feline Immunosupression

Two protocols are currently being used for the feline renal transplant recipient. In the first protocol, a combination of the Calcineurin inhibitor, CsA and the glucocorticoid, prednisolone are used together for their synergistic effects. Because the dose of cyclosporine that cats often require for immunosupression is small, an oral liquid formulation is used so that the dose can be titrated accordingly for each individual cat. Currently, the oral liquid formulation, Neoral (100 mg/ml), is recommended. Neoral is a microemulsified formulation and is preferred over the other oral liquid formulation, Sandimmune (Novartis Pharmaceuticals), because of better gastrointestinal absorption allowing for more predictable and sustained blood concentrations of the drug.⁶ Additionally, the dose of Neoral necessary to maintain therapeutic blood concentrations compared to Sandimmune is less, making the drug more economical for clients.

Depending on the transplant facility performing the procedure, CsA is typically begun 24 to 96h prior to transplantation. Depending on the cat’s appetite, Neoral is administered at a dose of 1 to 4 mg/kg PO q12h. In the author’s experience, cats that are anorexic or that are eating a minimal amount prior to surgery have a much lower drug requirement to obtain appropriate drug levels prior to surgery. A 12-hour whole-blood trough concentration is obtained one day prior to surgery to adjust the oral dose for the surgical procedure. A target 12-hour whole- blood trough concentration of 300 to 500 ng/ml prior to surgery using the technique of high-pressure liquid chromatography (HPLC) is recommended.¹⁵ This level is maintained for approximately 1 to 3 months following surgery and is then tapered to approximately 250 ng/ml for long term maintenance therapy. Prednisolone is administered beginning the morning of surgery. At our facility, prednisolone is started at a dose range of 0.5-1 mg/kg q12h orally for the first 3 months and then tapered over several weeks to q24h. Protocols for both CsA and prednisolone vary between transplantation facilities. Doses have ranged from 0.25 to 2.5 mg/kg PO q12h orally starting the morning of surgery and then tapering to 0.25 mg/kg PO q24h by 1 month following surgery^.2,3,15 Prednisolone is preferred over prednisone for immunosupression in the these patients. In an abstract evaluating the bioavailability and activity of these two drugs in cats, serum prednisolone levels were significantly greater for oral prednisolone than oral prednisone.¹⁶ It was suggested that these differences may be related to a decreased hepatic conversion of prednisone to prednisolone in some cats or decreased gastrointestinal absorption of prednisone.

A second protocol allows for once daily administration of medication. With this protocol, ketoconazole (10 mg/kg PO q24h) is administered in addition to the CsA and prednisolone.^17,18 Following the addition of ketoconazole, to the immunosuppressive protocol, CsA and prednisolone are administered once a day and CsA doses are adjusted into the therapeutic range by measuring 24 hour whole blood trough levels. Ketoconazole is an antifugal agent that can affect the metabolism of CsA by inhibiting both intestinal and hepatic cytochrome P450 oxidase activity resulting in increased blood CsA concentrations.¹⁸ This protocol may reduce the cost of immunosuppression following surgery as well as be more appealing for owners whose work schedule does not permit twice a day dosing of medication. If twice daily dosing is necessary, the ketoconazole dose can also be split and then added to twice daily regimens to reduce costs. Ketoconazole administration is discontinued if signs of hepatotoxicity are identified.

At our facility, high performance liquid chromatography (HPLC) is the method of choice for measurement of whole blood CsA concentrations. This technique measures only the parent compound and not the metabolites of CsA which can vary depending on the patients’ metabolism.¹⁹ Flurescent immunoassay methods using either monoclonal or polyclonal antibodies have also been used. Antibodies can cross-react with the metabolites of CsA resulting in higher and more variable CsA concentrations than results obtained using the HPLC method. Although the HPLC method is the preferred method for both human and veterinary patients, immunoassay methods can still be used. Using one immunoassay method (TDxFLx assay, Abbott Laboratories) in cats, an accurate estimation of the HPLC can be determined since the correlation between these 2 methods is very high in an individual cat.¹⁹ Whole blood CsA levels will be 1.5 to 4.2 times higher than levels measured with the HPLC method.^17,19 In a study evaluating CsA disposition following intravenous and multi-dose oral administration in cats, substantial individual variation of oral absorption was identified and results suggest that evaluation of 2-hour CsA blood concentration may be a better measure for estimating drug exposure than the 12-hour whole-blood trough concentration.²⁰ More work in this area is necessary prior to changing current drug monitoring protocols. Since CsA has a bitter taste, the medication is placed into a gelatin capsule prior to administration. If the owner is unable to medicate the cat, they should be given empty gelatin capsules to practice with until they feel comfortable with the technique. The capsule sizes that we most commonly use range from #1 to #3 depending on the dosage. The prednisolone, as well as other medication that the cat is taking, can be added to the gelatin capsule.

Both in vitro and in vivo studies have been performed evaluating the effects of various novel immunosuppressants such as tacrolimus, sirolimus, mycophenolate mofetil and leflunomide in cats, they have not been evaluated in the clinical patient.^21,22 Although these drugs may be effective for renal transplantation in cats, they are not without complication in the human transplant patient. Currently no other alternative immunosuppressive protocols exist for cats that cannot take CsA and prednisolone.

Canine Immunosupression

Canine transplantation remains a challenge with regard to determining the best immunosuppressive therapy, particularly in unrelated donor and recipient pairs. The selection of a major histocompatibility complex (MHC) identical littermate as a donor has been shown to improve long term graft survival in the recipient.⁶ Various immunosuppressive protocols are currently being used in both unrelated and related donor and recipient pairs with varying results. The combination of Neoral, prednisolone and azathioprine (Imuran, Glaxo Wellcome) has been found to successfully maintain renal allografts in both MHC match and mismatched donor and recipient pairs. In one study using 4 healthy, unrelated mongrel dogs, immunosupression using Neoral (20 mg/kg/day) combined with azathioprine (5 mg/ kg PO q48h) and prednisolone (1 mg/kg/day) resulted in 2 dogs surviving the 100 day study period, 1 dog being euthanized for an intestinal intussusception and 1 dog being euthanized for a severe upper respiratory infection.²³ The current dosage of Neoral recommended for dogs is 2.5-5 mg/kg PO q12h to attain a 12 hour whole-blood trough concentration of 500 ng/ml and 3 to 5 mg/kg PO q48h for azathioprine.⁶ Transplantation has also been successful in unrelated dogs with the addition of rabbit antidog antithymocyte serum to the CsA, azathioprine and prednisone regimen.²⁴ Finally, leflunomide has shown promise experimentally when combined with CsA. In a recent study evaluating MNA 715 (an immunomodulatory drug derived from leflunomide) and CsA in a mismatched dog transplant model, the combination of these 2 drugs significantly prolonged renal allograft survival and reduced the severity in histologic rejection.²⁵ MNA715 was administered at an initial loading dose of 4 mg/kg PO q24hr followed by a dose of 2 mg/kg PO q24hr.

Anesthetic Protocols for Recipient and Donor

The specific anesthetic protocol for these patients is not unique to this surgical procedure, however there are important concepts to be emphasized. An example of a donor and recipient anesthetic protocol that have been successfully used at our hospital is presented (Table 29-7). The reader is also referred to a recent publication on anesthetic management in feline renal transplantation.²⁶ At the time of anesthetic induction, both the donor and recipient cats are given cephalexin (22 mg/kg IV q2h). Additionally, an epidural injection is performed on both cats (Bupivicaine [0.1 mg/kg] and Morphine [0.15 mg/kg]) for analgesia. Both cats may be under anesthesia for as long as 4 to 6 hours and hypothermia is of serious concern and can be detrimental to these patients. A circulating warm air blanket is used throughout the procedure and continuous monitoring of esophageal temperatures is performed. In addition to cephalic catheters, an indwelling double lumen jugular catheter is placed into the recipient right jugular vein so that venous blood gases, the PCV and TP as well as the electrolytes can be monitored throughout surgery. The left side of the neck is preserved in animals where an esophagostomy tube may be placed. Additionally, at the time of anesthetic induction, the recipient is given a unit of cross-match compatible whole blood from the kidney donor followed by other cross-match compatible blood products as needed. The donor cat is administered mannitol on 2 occasions during the surgical procedure; 0.25 g/kg IV at the time of the abdominal incision and 1 g/kg 20 minutes prior to nephrectomy. Mannitol (0.5-0.1 g/kg IV) is occasionally administered to the recipient if there is concern regarding allograft perfusion following vascular anastomosis. Systemic arterial blood pressure is monitored regularly in both cats non-invasively via a Doppler technique and hypotension corrected by decreasing the concentration of inhalant anesthetic, or by the administration of fluid boluses, blood products or a continuous infusion of dopamine (5 ug/kg/min). Intraoperative hypertension can be treated successfully with the SQ administration of hydralazine (2.5 mg SQ for a 4 kg cat).
 

Renal Transplantation Surgery

Successful renal transplantation in the cat requires an operating microscope and surgical experience with microsurgical vascular and ureteral surgical procedures.

Feline Surgical Technique

In our hospital, 3 surgeons are required for each transplant procedure; 2 surgeons to operate on the donor and recipient and a third surgeon to close the donor following the nephrectomy. The donor cat is brought into the surgical suite approximately 45 minutes prior to the recipient and the donor kidney prepared for nephrectomy. At the time of initial incision, the donor is given a dose of mannitol (0.25 g/kg IV over 15 minutes). The alpha adrenergic agonist acepromazine (0.1 mg/kg IV) has also been recommended by some surgeons.¹⁷ These drugs are used to minimize renal arterial spasms, improve renal blood flow and protect against renal tissue injury that can occur during the warm ischemia period. It is essential to harvest a donor kidney with a single renal artery. Many renal arteries bifurcate close to the kidney. A minimal length of 0.5 cm of a single renal artery is necessary for the arterial anastomosis.⁶ The CT angiography that was performed on the donor prior to anesthesia not only provides important information regarding the renal vasculature, but also prevents delays between the donor nephrectomy and recipient anesthesia induction. The left kidney is preferred as a donor because it provides a longer renal vein than the right kidney. In most situations, if two renal veins are present, the smaller vein can be sacrificed. Prior to sacrificing a small vein, however, it is important for the surgeon to identify the ureteral vein and determine that it is not draining into the renal vein that is being sacrificed. The renal artery and vein are cleared of as much fat and adventitia as possible and the ureter is dissected free to the point where it enters the bladder serosa. Using sterile paper, templates are made of both the donor renal artery and vein to determine the size of the venotomy and aortotomy to be performed in the recipient. Harvesting the donor kidney is performed when the recipient is fully prepared to receive the kidney. Fifteen minutes prior to nephrectomy, a 2nd dose of mannitol (1.0 g/kg IV) is given to the donor cat.

An operating microscope is used for the majority of the recipient surgery. Following a full abdominal exploratory, the colon and ileum are tacked to the body wall using 3-0 chromic gut to aid in surgical exposure. Two surgical methods of renal transplantation have been described. The first technique described transfers the transplanted kidney to the recipient’s iliac vessels. In this technique, an end-to-end arterial anastomosis of the external iliac and renal artery and an end-to-side anastomosis of the external iliac vein and renal vein are performed.² Approximately 12% of cats having this procedure developed pelvic limb complications including pain, hypothermia, edema, paresis and paralysis.⁵ These complications have been successfully prevented by changing the vascular surgical technique. In the revised procedure, the renal artery is anastomosed end-to-side to the caudal aorta (proximal to the caudal mesenteric artery), and the renal vein is anastomosed end-to-side to the caudal vena cava (Figure 29-22A and B).²⁷ Partial occlusion vascular clamps are used to obstruct blood flow in both the aorta and the caudal vena cava. Using the previously made templates from the donor vessels, windows are created in both the aorta and vena cava that match the size of the renal artery and vein, respectively. An aortotomy clamp is used to create the stoma in the aorta and adventitial scissors are used to create an oval defect in the vena cava. The aorta and vena cava are flushed with a heparinized saline solution. Two sutures of 8-0 nylon are placed at the cranial and caudal aspect of the aortotomy site. Sutures are not pre-placed in the venotomy.
 

Following the second mannitol infusion in the donor, the graft is harvested and flushed with a phosphate-buffered sucrose preservation solution. Excess adventitia on the end of the renal artery is excised and the artery dilated. The renal artery is anastomosed to the aorta using 8-0 nylon in 2 rows of simple continuous sutures; one on the medial aspect and one on the lateral aspect of the artery. The renal vein is anastomosed to the vena cava using 7-0 silk. A back wall technique is used first to suture the portion of the renal vein closest to the renal artery. The anastomosis is completed once the second side of the vein is sutured using a continuous pattern. The venous clamp is removed first and then the arterial clamp. Some hemorrhage may occur but typically can be controlled with direct pressure. Significant leaks are repaired with the placement of additional single interrupted sutures. Occasionally, renal arterial spasm can occur following release of the vascular clamps. The application of topical lidocaine or acepromazine has been effective in some cases in eliminating this problem. Others recommend the systemic use of chlorpromazine or acepromazine for treating the vascular spasms that can occur and have found these drugs to be more effective than lidocaine.¹⁷ In a comparison of the two surgical techniques, although not statistically significant, the graft warm ischemia and total surgical times were shorter using the arterial end-to-side technique compared to the iliac vessel technique. Additionally, pelvic limb complications were not identified using the revised technique.²⁷

An alternative to performing the donor and recipient surgeries simultaneously is the use of hypothermic storage to preserve the donor kidney until the recipient surgery is performed. Following preparation of the donor kidney within the donor, a nephrectomy is performed and the graft flushed with a phosphate-buffered sucrose organ preservation solution.¹⁷ To perform this technique, the renal artery is cannulated with an 18-gauge catheter, perfused with 25 to 50 ml of preservation solution at 100 cm water pressure and then placed in a stainless steel bowl which contains approximately 200 ml of preservation solution. The bowl is floated in an ice slush, the kidney agitated until cold to the touch and the bowl is covered with a sterile drape.^17,28 This technique is preferred by some surgeons because it reduces personnel and resources needed for the transplantation procedure and the cold preservation technique has been found to minimize ischemic injury that can occur to the kidney.

Once the vascular anastomosis is complete, a ureteroneocystotomy is performed. Three techniques have been described and are currently being performed at different surgical centers. I prefer the intravesicular mucosal apposition technique.³ With this technique, a ventral midline cystotomy is performed. A mosquito hemostat is used to make a hole at the apex of the bladder and then the end of the ureter is grasped and brought directly into the bladder lumen. Tunneling of the ureter through the bladder wall is not performed (Figure 29-23). The bladder is everted, the distal end of the ureter is excised, periureteral fat removed and then the end of the ureter is spatulated a distance of 0.5-0.75 cm (Figure 29-24). The ureteral mucosa is sutured to the bladder mucosa using either 8-0 vicryl or 8-0 nylon in a simple interrupted pattern. The first and most critical suture is placed at the proximal end of the ureteral incision (point of the “V”) (Figure 29-25) It is important that no periureteral fat is exposed once suturing is complete as this can lead to adhesions and granuloma formation potentially resulting in a ureteral obstruction. A 5-0 polypropylene suture can be used to check for ureteral patency. Following completion of the anastomosis, the bladder is closed with absorbable suture in a single layer appositional pattern.
 

Two newer techniques for ureteral implantation, both extravesicular, have recently been described. In the first technique (Figure 29-26), a 1 cm incision is made through the seromuscular layer on the ventral surface of the bladder allowing the mucosa to bulge through the incision.^6,29 A smaller incision (3 to 4 mm) is made through the mucosal layer of the bladder at the caudal aspect of the seromuscular incision. The distal end of the ureter is prepared as previously described. Ureteral mucosa is sutured to bladder mucosa using 8-0 vicryl or nylon. The proximal and distal sutures are placed first. Similar to the previous technique, 5-0 polypropylene suture can be used to check for ureteral patency. Once the ureteral anastomosis is complete, the seromuscular layer is apposed in a simple interrupted pattern over the ureter using 4-0 absorbable suture such as PDS. In the second technique, the entire ureter and ureteral papilla are harvested and sutured using an extravesicular technique.³⁰ A 2 mm cuff of bladder wall is isolated along with the distal end of the ureter. A 4 mm defect is made at the apex of the bladder and the ureteral papilla sutured in place using 8-0 Vicryl in a 2 layer pattern; mucosa to mucosa and seromuscular layer to seromuscular layer.

Prior to abdominal closure of the recipient, a biopsy of one of the native kidneys is taken (if not previously performed) and an esophagostomy tube placed if nutritional support is deemed necessary. Finally, the allograft is pexied to the abdominal wall. If the kidney is transplanted onto the aorta and vena cava, the adjacent body wall is incised and the incised edge sutured to the renal capsule using 6 interrupted sutures of 4-0 polypropylene. Another procedure involves the creation of a musculoperitoneal flap (based ventrally) which is elevated from the adjacent body wall and sutured to the renal capsule using 4-6 interrupted sutures of 5-0 polypropylene.⁶ The pexy is critical to prevent allograft torsion on its vascular pedicle causing ischemia and subsequent graft loss. The native kidneys are usually left in situ to act as a reserve if graft function is delayed. If warranted, the kidneys can be removed at a later time. In cases of polycystic kidney disease, often one of the native kidneys needs to be removed at the time of the transplantation procedure in order to make room in the abdomen for the allograft.
 

Canine Surgical Technique

The surgical techniques described for renal transplantation in the dog are similar to those described for the cat with minor differences. Both the iliac vessel technique as well as anastomosing the renal vasculature to the caudal aorta and vena cava have been performed successfully in the dog and unlike the cat, magnification may not be necessary depending on the size of the patient.⁶ Unlike cats, the iliac vessel technique is still being used both experimentally and clinically in the dog. The selected iliac artery is prepared for an end-to-end anastomosis to the renal artery and the external iliac vein is prepared for an end-to-side anastomosis to the renal vein. A bulldog vascular clamp is placed near the aortic bifurcation to occlude the iliac artery. The artery is subsequently ligated distally, severed and then flushed with heparinized saline solution. The end of the artery is dilated slightly and cleaned of any excess adventitia. The external iliac vein is isolated in the same region, tributary veins ligated and then 2 bulldog vascular clamps placed as far apart as possible (first distally and then proximally). A partial occlusion clamp can also be used. A venotomy in the external iliac vein is performed and then 2 rows of simple continuous sutures are used on the medial and lateral aspect of the renal vein and iliac vein as previously described for the cat. The renal artery and iliac artery are anastomosed using a simple interrupted pattern. Suture material used for the vascular anastomoses is 4-0 to 6-0 silk for the venous anastomosis and 5-0 to 8-0 nylon or polypropylene for the arterial anastomosis. Both intravesicular and extravesicular techniques for ureteroneocystostomy have been used successfully in canine transplantation. The renal capsule of the allograft is sutured to the abdominal body wall with simple interrupted sutures of 3-0 polypropylene, with a musculoperitoneal flap (based ventrally) using 3-0 polypropylene or by suturing the allograft capsule to the adjacent mesocolon with simple interrupted sutures of 3-0 polypropylene.^6,24

Postoperative Care and Perioperative Complications

Important points of postoperative care in the transplant patient include minimizing stress and handling of the patient and treatment of hypothermia. The recipient is administered a balanced electrolyte solution with the volume adjusted depending on the cat’s hydration status and oral intake of water. Blood transfusions should be given as needed. The cat is maintained on IV antibiotic therapy (cefazolin, 22 mg/kg IV q8h) until the intravenous catheter is removed and then the cat is maintained on oral amoxicillin combined with clavulenic acid (Clavamox, 62.5 mg PO q12h) until the feeding tube is removed. If the cat is Toxoplasma positive, Clindamycin (25 mg PO q12hr) is administered and continued for the lifetime of the cat. Postoperative pain has been controlled successfully using either hydromorphone (0.1-0.2 mg/kg IM or SQ q4-6h), buprenorphine (0.005-0.02 mg/kg IV q4-6h) or a constant rate infusion of butorphanol (0.1-0.5 mg/kg/h). An extended data base evaluating the packed cell volume, total protein, electrolytes, blood glucose and acid base status is initially evaluated 2 to 3 times daily and then tapered accordingly depending on the patient’s stability. A renal chemistry panel is checked every 24 to 48 hours and a blood CsA level is checked every 3 to 4 days. The oral CsA dose is adjusted accordingly depending on postoperative blood levels. It has been the author’s experience that CsA requirements typically decrease in the early postoperative period, likely associated with preoperative fasting of the patient and postoperative anorexia. The prednisolone dose is continued as previously described (0.5 to 1 mg/kg PO q12h). Voided urine is collected daily to assess urine specific gravity. Typically with appropriate pain control and improvement in azotemia, most cats start eating within 24 to 48 hours following the surgical procedure. In some cases in which continued anorexia is thought to be associated with altered gastric motility following surgery, metoclopramide administration (0.2 mg/kg SQ q6-8h) has been successful in improving a cat’s appetite. If the cat remains anorexic, feeding is begun using the esophagostomy tube. Feeding is continued until the cat is eating and drinking and then tapered accordingly.

Patients are monitored for postoperative seizure activity every 1 to 2 hours for the first 3 days. During the 1990’s, the most common complication reported in cats during the perioperative period was central nervous system (CNS) disorders including disorientation and seizures which occasionally progressed to a comatose state as well as respiratory and cardiac arrest.³¹ In one report, the median time until onset of seizure activity was 24 hours following surgery.⁵ Many variables were evaluated and showed no difference between affected and unaffected cats with respect to the degree of azotemia, magnesium and cholesterol levels, intraoperative blood pressure, osmolality, serum electrolyte and blood glucose concentration, erythropoietin and CsA administration.^7,31 In one study, postoperative hypertension was identified as a major contributing factor to postoperative seizure activity in the feline renal transplant recipient.³² Additionally, the administration of antihypertensive therapy significantly reduced the seizure frequency and the morbidity and mortality associated with neurologic complications. Because of these findings, during the first 48 to 72 hours, indirect blood pressure is monitored every 1 to 2 hours for the development of hypertension. If the systolic blood pressure is equal to or exceeds 170 mmHg, hydralazine (Sidmack Laboratories, 2.5 mg SQ) is administered. The hydralazine dose can be repeated if the systolic pressure hasn’t decreased within 15 minutes. If the cat is refractory to hydralazine, acepromazine (0.005-0.01 mg/kg IV) has been used successfully. It is important to note that the cause of CNS disorders in human transplant patients is thought to be multifactorial, and since there appears to be a difference between transplant centers in the incidence of hypertension and CNS disorders, the occurrence of CNS disorders in cats following renal transplantation remains a challenge.¹⁷ Postoperative hypotension may also produce complications. Systolic blood pressure should be maintained at equal to or greater than 100 mmHg. Sustained hypotension can be a serious problem leading to poor graft perfusion. These patients need to be treated aggressively to prevent acute tubular necrosis and delayed graft function.

If transplant surgery is technically successful, azotemia typically resolves and the cat improves clinically within the first few days following surgery. If improvement is not identified during this time or if improvement in renal function as well as the clinical status of the patient is initially identified, but then worsens, an ultrasonographic examination of the allograft is warranted. The allograft should be evaluated for any signs of hydronephrosis and hydroureter as well as renal blood flow. If ureteral obstruction is suspected, the cat is anesthetized and the allograft ureter evaluated. In some cases, the ureter may need to be re-implanted into the urinary bladder. If graft perfusion is adequate and no hydronephrosis/hydroureter exists, delayed graft function may be occurring. Typically, if perfusion remains adequate, improvement in graft function often occurs within the first few weeks following surgery. The author suspected delayed graft function in one cat and significant improvement didn’t occur for approximately 6 to 8 weeks postoperatively. This cat experienced prolonged episodes of hypotension during surgery as well as in the immediate postoperative period.

Normally, without major complication, the recipient is transferred from the intensive care unit to the renal transplantation ward within a few days following surgery. Patients are discharged when graft function appears adequate and CsA blood levels are stable. If otherwise stable, cats with a delay in function of their graft can also be discharged. Medical management can be continued in this subset of patients until graft function returns to normal. If the transplanted kidney fails to function, the kidney should be biopsied prior to attempting retransplantation of the patient.

Long-Term Management and Complications

Following discharge, both cats should be evaluated by the primary care veterinarian once a week for the first 4 to 6 weeks initially and then extended to monthly intervals if the cat is clinically stable. During each exam, a renal panel, packed cell volume, total protein, a cyclosporine level and a urinalysis of a free-catch urine sample is performed. Body weight should be monitored regularly. It is recommended that a complete blood count and serum chemistry panel be performed every 3 to 4 months and an echocardiography performed every 6 to 12 months if the cat had been diagnosed with underlying cardiac disease prior to transplantation. The feeding tube can be removed at suture removal if oral intake of food and water is appropriate.

There is seemingly little correlation between the oral dose of cyclosporine and the blood level that will be achieved in an individual animal. Cats of similar weight on identical doses of CsA may vary markedly in blood levels achieved. Because of individual patient variability in the absorption of oral cyclosporine and its metabolism, it is essential that blood levels are monitored regularly to maintain therapeutic concentrations and minimize side effects from toxicity. As previously described, CsA trough levels are maintained for approximately 1 to 3 months following surgery at 300 to 500 ng/ml and then tapered to approximately 250 ng/ml for maintenance therapy. Although rare, a fatal side effect of CsA therapy, hemolytic uremic syndrome (HUS), has been identified in the cat.³³ Patients develop hemolytic anemia, thrombocytopenia with rapid deterioration of renal function secondary to glomerular and renal arteriolar platelet and fibrin thrombi. Unfortunately, the disease typically has not manifested itself until after the transplant procedure and the mortality rate has been 100%.

If renal function remains normal following transplantation, the anemia associated with renal failure should resolve within 3-4 weeks after surgery.³⁴ If graft function remains adequate, but the anemia persists, iron supplementation should be considered.

Renal complications following transplantation have included renal rejection, hemolytic uremic syndrome, oxalate nephrosis and renal failure. Both acute and chronic rejection have bee described in the cat. Acute rejection with loss of function of the affected organ can occur at any time, but is most common within the first 1 to 2 months following surgery. Acute rejection is often associated with poor owner compliance in administration of required medication. Some cats that are experiencing a rejection episode may be lethargic, depressed, anorexic and PU/PD and thus prompt a visit to a veterinarian while in other cats, clinical signs may be minimal. For this reason, weekly blood sampling is critical during this time period to detect any changes in serum creatinine concentration. Histopathologic, sonographic, and scintigraphic examination of allograft rejection in cats has recently been described.^35,36 In one study, allograft histopathology revealed significant interstitial inflammation and tubulitis with varying degrees of intimal arteritis.³⁵ A significant increase in cross sectional area of the kidney on ultrasound examination has been identified in cats during a rejection episode.³⁶ Although normal allograft enlargement is expected during the first week postoperatively, a gradual decline in size should then occur. Allograft rejection should be suspected if renal enlargement persists or progresses beyond 7 days. Additionally, a subjective increase in echogenicity and a decrease in corticomedullary demarcation may be identified in allografts undergoing rejection.³⁶ Neither resistive index nor glomerular filtration rate were sensitive indicators in normal grafts and those undergoing allograft rejection.^36-38 Prior to initiating treatment for rejection, a urine sediment should be evaluated to rule out obvious infection and an abdominal ultrasound performed of the allograft to rule out ureteral obstruction.

Treatment for a possible rejection episode should not be delayed and these tests should only be performed prior to initiating therapy if in house capabilities are available. Acute rejection episodes are treated with intravenous administration of cyclosporine (6.6 mg/ kg q24h given over 4 to 6h) and prednisolone sodium succinate (Solu Delta Cortef, Upjohn, 10 mg/kg IV q12h). Each milliliter of the IV cyclosporine is diluted with 20 to 100 ml of either 0.9% NaCl or 5% Dextrose (not Lactated Ringer’s solution). Because CsA is light sensitive, the IV fluid lines should be covered. Following the completion of the CsA infusion, the cat is continued on IV fluid therapy. The infusion of CsA can be repeated, however if the creatinine concentration does not improve within 24 to 48 hours, other causes for the azotemia should be investigated. Chronic rejection is characterized by a gradual loss of organ function over months to years, often without a known episode of rejection. Kidneys undergoing chronic rejection show severe narrowing of numerous arteries and thickening of the glomerular capillary basement membrane. Unfortunately, the cause of chronic rejection is undetermined. As described previously, HUS is a rare, but fatal complication in the feline renal transplant recipient. Three feline transplant recipients were dignosed with HUS secondary to cyclosporine therapy.³³

Results of a recent study suggest that transplantation is a treatment option for cats with calcium oxalate (CaOx) urolithiasis. No difference in long term outcome was found between a group of 13 cats with CaOx calculi and a control group of 49 cats whose underlying cause of renal failure was not related to calculi formation.⁹ Although formation of calculi in the allograft did not significantly reduce survival, the power of the study was low and there was a trend towards lower survival rates in cats that formed calculi. Four of the 5 cats that formed calculi following surgery had calculi attached to the nylon suture used to perform the ureteroneocystostomy and two cats that formed calculi after surgery were diagnosed with a urinary tract infection. We speculate and recommend that the use of absorbable suture material for performing the ureteroneocystostomy and a more thorough screening for urinary tract infection be performed in these cats.

Another potential cause for the recurrence of azotemia in the first few months postoperatively in the feline renal transplant recipient is the development of retroperitoneal fibrosis.³⁹ The cause is unknown but may be associated with operative trauma, infection, the presence of foreign material, inadequate immunosupression, hemorrhage or urine leakage during the transplant procedure. Ultrasound examination of the kidney reveals hydronephrosis with or without hydroureter and occasionally, a capsule can be identified surrounding the allograft. Surgery has been successful in relieving the obstruction and restoring normal renal function.

Finally, similar to humans following transplantation, complications occur secondary to chronic immunosuppressive therapy. Cats and dogs are more susceptible to bacterial and fungal infections as well as opportunistic infections such as the reactivation of latent Toxoplasma gondii infection.¹² Bacterial urinary tract infections in the transplant patient cause direct morbidity and mortality due to the infection itself, and may also activate the rejection process. Two cats have developed fatal Mycobacterium infections following chronic immunosuppressive therapy; one cat had systemic disease and the other cat had septic arthritis.^{40,(personal communication, Aronson 2005)} Transplant recipients are also more susceptible to various forms of neoplasia and diabetes. Decreased immune surveillance, activation of latent oncogenic viruses such as the Epstein Barr virus and chronic antigenic stimulation are thought to put human patients at increased risk for various forms of neoplasia.⁷ The prevalence of neoplasia in cats following renal transplantation has been reported from 9.5 to 14% with lymphoma being the most common type reported.⁴¹

Conclusion

Renal transplantation offers a unique method of treatment for renal failure in cats. Currently, approximately 90 to 95% of cats recover from surgery sufficiently to be discharged to the owner and approximately 70% of these cases are alive and clinically doing well 1 year after transplant. Transplant success in the canine is considerably less than the feline unless matched donors and recipients are used. Survival times have steadily improved as more animals have been treated and careful screening of recipients is performed, and early recognition of problems and complications has improved. Clients interested in renal transplantation for their pet need to understand the risks of surgery and recovery and that substantial ongoing care is necessary for the life of the animal.

References

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Introduction

Ureteral ectopia is a complex congenital abnormality of the urinary system frequently resulting in urinary incontinence. Distal displacement of one or both ureteral orifice(s) to sites within the bladder neck, urethra, vagina or vestibule has been described in small animal patients. Intermittent, continual or positional urinary incontinence is the most common clinical symptom reported in both juvenile and adult patients diagnosed with ureteral ectopia. Ureteral ectopia is diagnosed with significantly greater frequency in females compared to males in all affected species. Ureteral ectopia is reported in both purebred and mix-breed dogs. It has been documented with greater frequency in specific breeds including Labrador retriever, Golden retriever, Siberian husky, Newfoundland, Skye terrier, West Highland white terrier, Wire-haired fox terrier, Soft-Coated Wheaten terrier as well as Standard and Miniature poodles. The specific etiology of this developmental anomaly remains unclear and a genetic basis has not yet been established.

Two types of ectopic ureters are recognized in veterinary patients based on the anatomic structure and pathway of the distal ureter. Extramural ureters exit the kidney and completely bypass the bladder opening directly into the proximal, middle or distal urethra, uterus, vagina or vestibule. The incidence of extramural ectopic ureters is rare. Intramural ectopic ureters attach to the serosal surface of the bladder in the expected dorsolateral anatomical position, yet fail to open into the bladder lumen at the tip of the trigone. Intramural ectopic ureters tunnel submucosally through the trigonal region to open at sites within or distal to the bladder neck. Intramural ectopic ureters are the most common type of ectopic ureters identified in both male and female dogs. Additional anatomic variations of the distal ureteral segment include multiple fenestrations, ureteral troughs, dilation, branched ureters and associated ureteroceles. Urinary incontinence since birth or following ovariohysterectomy is the most frequently reported clinical symptom in patients diagnosed with ureteral ectopia. Normal voiding patterns may also be observed in these patients. The cause of urinary incontinence is considered multifactorial. It can result from urine outflow distal to the bladder neck and urethral sphincter mechanism,or functional and/or structural abnormalities of the vesicourethral junction and urethra resulting in primary sphincter mechanism incompetence. The degree of urinary incontinence and patterns of urination cannot be used to confirm the diagnosis of ureteral ectopia nor determine if unilateral or bilateral disease exists.

Diagnosis

Ureteral ectopia is the most common cause of urinary incontinence in young female dogs. However, it should also be considered as a rule-out for patients with history of incontinence after ovariohysterectomy. Physical examination is often normal with the exception of moist or urine stained hair in the perivulvar or prepucial region. 

Perivulvar or prepucial dermatitis secondary to urine scalding may be observed. Careful abdominal palpation is performed to discern marked abnormalities in kidney size that can result from hydronephrosis or dysplasia. Results of hematological and serum biochemical evaluations are often normal unless associated abnormalities of the upper urinary tract that diminish renal function exist. Urinary tract infections are frequently identified resulting from ascending bacterial pathogens.

The specific diagnosis of ureteral ectopia is based on identification of one or both ureteral orifice(s) in a distally displaced position. Uroendoscopy or direct visualization at surgery is considered to be the “gold standard” for the diagnosis of ureteral ectopia in female dogs. Direct visualization of the lumenal surface of the lower urinary and reproductive tracts using a rigid or flexible endoscope has dramatically improved our ability to accurately diagnose and classify ectopic ureters and identify associated abnormalities in a minimally invasive manner. Radiographic imaging techniques including intravenous urography (IVU) with or without fluoroscopy, vaginocystography, contrast enhanced computed tomography (CT) and ultrasonography may also provide a valuable method of diagnosis as well as providing valuable information regarding structure and function of the urinary tract. Specific identification of the ureteral orifice with imaging techniques can be difficult or obscured by contrast accumulation in the urinary bladder resulting in a potential false positive or false negative diagnosis.

Surgical Techniques

The goal of surgical treatment of ureteral ectopia is resolution of urinary incontinence and re-establishment of anatomical integrity of the lower urinary system. The specific surgical correction of ureteral ectopia is based upon location and morphology of the ectopic ureter(s), and associated abnormalities of the urogenital tract. A variety of urologic abnormalities have been reported associated with ureteral ectopia including renal dysplasia, renal agenesis, hydronephrosis, hydroureter, tortuous ureter and presence of a septal remnant at the opening of the cranial vaginal vault. Evaluation of renal structure and function is an essential part of the surgical planning. Ultrasonographic evaluation of the upper urinary structures combined with either contrast radiography (IVU) or differential renal nuclear scintigraphy is performed to characterize renal function. Nephroureterectomy is performed when a kidney is determined to be nonfunctional. Renal biopsy and culture are recommended if structural abnormalities of a functional kidney are noted.

Ureteral Reimplantation

Extramural ectopic ureters may result in persistent incontinence because the ureteral orifice is positioned distal to the bladder neck and urethral sphincter mechanism (Figure 29-27A). Repositioning the ureteral orifice directly into the bladder may restore urinary continence provided additional functional or structural abnormalities of the urethral sphincter mechanism do not exist.

The urinary bladder and proximal urethra are exposed and isolated. The distal aspect of the extramural ectopic ureter is isolated at the site of attachment to the dorsolateral surface of the vesicourethral junction, urethra, uterus or vagina. The extramural ureter is ligated at its distal point of attachment with 3/0 absorbable suture material and the ureter transected cranial to the ligature (Figure 29-27B). The surgeon should gently isolate the distal 1/3 of the ureter from the ureteral fascia and retroperitoneal space avoiding disruption of the ureteral arterial blood supply located longitudinally within the fascial attachment. The site of ureteral reimplantation is determined by examining bladder size and position without traction and relative to ureteral length. Ureteral reimplantation can be performed at any site within the bladder between the apex and the tip of the trigone however it is critical to avoid tension at the vesicoureteral anastomosis. A ventral midline cystotomy is performed and a small mucosal incision or defect created at the proposed site of ureteral reimplantation. A mosquito hemostat is passed through the mucosal incision at an oblique angle to exit the serosal surface of the bladder. The surgeon then gently guides the ureter through the bladder wall defect (Figure 29-27C). Once positioned within the bladder lumen, the terminal .25 cm of the ureter is excised and discarded. If the ureteral orifice is extremely small, magnification should be used to accurately place the ureterovesicular anastomotic sutures. Alternatively, the terminal end (4 to 6 mm) of the ureter can be incised longitudinally with small metzenbaum scissors to spatulate or widen the orifice to facilitate the intravesicular anastomosis (Figure 29-27D). Intravesicular ureteral anastomosis is accomplished by suturing the ureteral mucosa to the incised edges of the bladder mucosa using 4 to 6 interrupted 5-0 absorbable, monofilament sutures (Figure 29-27E). The bladder is closed in a routine manner with a 4-0 absorbable monofilament suture material in a one or two layer closure.
 

Neoureterostomy and Urethral/Trigonal Reconstruction

Urinary incontinence caused by an intramural ectopic ureter is attributed to both the ectopic position of the ureteral orifice and/or malformation or dysfunction of the proximal urethral sphincter mechanism by the submucosal ureter. Historically, surgical repair of intramural ectopic ureters has focused on the creation of a new ureteral opening within the bladder lumen and ligation of the distal submucosal ureteral remnant. Persistent or recurrent urinary incontinence after surgery has been frequently reported after this surgery. To restore the functional anatomy of the internal urethral sphincter mechanism in an effort to improve continence after surgery, the terminal segment of the intramural ureter is resected from the surrounding tissues of the bladder neck and urethra. Surgical apposition of the urethral mucosa and smooth muscle layers of the remaining defect are performed to realign the smooth muscle layer of the internal urethral sphincter mechanism.

A ventral midline cystotomy and urethrotomy is performed to expose the trigone and intramural ureter(s). Most displaced ureteral orifices are visualized distally within the bladder neck or urethra (Figure 29-28A). However, if a displaced ureteral orifice is located distally beyond the extent of this approach, a small incision can be made through the urethral mucosa into the lumen of the submucosal ureter to create an orifice avoiding the surgical morbidity of pelvic osteotomy. An appropriate sized (5,8 or 10 French) soft urethral catheter is passed retrograde through each displaced ureteral orifice (Figure 29-28B). With the catheter in place, the ureter is sharply dissected from the surrounding urethral tissues including the mucosa, submucosa and muscularis using small metzenbaum scissors. Surgical dissection through the seromuscular layer on the dorsal aspect of the urethra should be avoided. Primary closure of the mucosal/ submucosal defect created by dissection in the bladder neck and urethra is performed using 4 or 5-0 synthetic absorbable, monofilament suture material in a continuous pattern. Closure of the urethral mucosa including a deep bite of the underlying smooth muscle layer is performed. Hemorrhage is controlled by placement of the suture pattern to close the defect. It may be necessary to dissect a portion of the submucosal ureter followed immediately by closure of the defect to control hemorrhage before continuing with the complete dissection (Figure 29-28C). The ectopic ureter is completely dissected from its submucosal position distally to the site where the ureter passes through the bladder wall. The ureteral remnant is transected approximately .5 cm from the site where the ureter passes through the bladder wall. To create a new permanent ureteral opening within the bladder, the ureteral mucosa is sutured to the bladder mucosa using 5-0 absorbable suture in an interrupted pattern (Figure 29-28D). An appropriate size soft urethral catheter can be passed from the bladder lumen distally to exit the vulva. The tip of an appropriate size balloon tipped urinary catheter is carefully sutured to the tip of the red rubber catheter protruding from the vulva with a silk suture. The urethral catheter is withdrawn into the bladder lumen to facilitate the passage of the balloon tipped catheter through the urethra during surgery. The urethral catheter is detached and discarded and the catheter balloon inflated with saline. The cystotomy and urethrotomy are closed using 4-0 absorbable monofilament suture in a single or double layer continuous or interrupted pattern.

The urinary catheter and a closed urine collection system should be maintained for 24 to 48 hours after surgery. Following removal of the urethral catheter, stranguria may be noted. Administration of NSAID therapy can be considered if renal function is normal.
 

Nephroureterectomy

Removal of a nonfunctional, dysplastic or hydronephrotic kidney with a severely dilated ectopic ureter is indicated as a salvage procedure provided renal function in the contralateral kidney is normal. Aerobic bacteriologic cultures from the renal pelvis should be obtained if a urinary tract infection is diagnosed prior to surgery or pyelonephritis is suspected. Perform a ventral midline celiotomy from xyphoid to pubis. Gently free the kidney from its retroperitoneal attachments and reflect it medially to expose the vascular pedicle and ureter at the dorsal aspect of the renal hilus. Bluntly dissect the perirenal fat from the renal hilus to expose the vascular pedicle. Isolate and doubly ligate the renal artery and vein individually with an appropriate sized silk suture. An additional transfixation suture is placed through the renal artery and the renal artery and vein transected. Sharply dissect the ureter from the ureteral fascia and retroperitoneal space to its termination. The ureter is ligated at its most distal point of attachment with a 3-0 absorbable suture and transected cranial to the ligature. Nephroureterectomy without the removal of the associated intramural ureteral remnant will likely result in continued incontinence after surgery. A ventral midline cystotomy and urethrotomy is performed to identify and remove the submucosal remnant of the ectopic ureter as previously described.

Post-Surgical Considerations

Mild to moderate ureteral dilation occurs following surgical manipulation of the ureter and generally resolves within 4 to 6 weeks after surgery. However, moderate to severe hydroureter, present prior to surgery, is most likely a developmental response of the ureter to increased lower urinary tract outflow pressure. Successful surgical correction of ureteral ectopia may improve but will not completely resolve the hydroureter in this situation.

Persistent urinary incontinence is the most common complication after surgical repair of unilateral or bilateral ureteral ectopia. Urinary incontinence has been reported to occur in 44 to 67% of patients undergoing either ureteral reimplantation, neoureterostomy or ureteronephrectomy alone. Patients with continuous or recurrent symptoms of urinary incontinence should be completely evaluated for additional causes of incontinence including urinary tract infection,other congenital abnormalities of the urogenital tract and primary sphincter mechanism incompetence. Aerobic bacteriologic cultures of urine samples obtained via cystocentesis should be performed and appropriate antibiotic therapy administered based on results of antibiotic sensitivity testing. Alpha-adrenergic drugs such as phenylpropanolamine, ephedrine sulfate and oxybutinin have been used successfully to manage some patients with mild urinary incontinence after surgery. An additional consideration for patients with unrelenting urinary incontinence after appropriate surgical correction of the ureteral ectopia, is the use of endoscopically placed urethral submucosal bulking agents such as bovine collagen to treat the sphincter mechanism incompetence.

Editor’s Note: Until recently, surgical correction has been the primary treatment for ectopic ureter. Surgical correction is challenging and a high degree of technical skill is required. Surgical time, patient pain, and required hospitalization are potential disadvantages. Cystoscopic laser ablation performed by minimally invasive techniques has shown promising results. Cystoscopic capability and laser access are required. Consultation with an internist at a referral center is recommended.

Suggested Readings

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Dean P.W., Bjorab M.J., Constantinescu G.M.: Canine ectopic ureter. Compend Contin Educ Pract Vet 10(2):146, 1988.

Lane I.F., Lappin M.R., Seim H.B.: Evaluation of results of preoperative urodynamic measurements in nine dogs with ectopic ureters. J Am Vet Med Assoc 206:1348, 1995.

Leveille R., Atilola M.A.: Retrograde vaginocystography: A contrast study for evaluation of bitches with urinary incontinence. Compend Contin Educ Pract Vet 13:934, 1991.

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McLoughlin M. A., Chew D.J.: Diagnosis and surgical management of ectopic ureters. Clin Tech Sm Anim Pract 15:17, 2000.

Mason L.K., Stone E.A., Biery D.N., et al.: Surgery of ectopic ureters: Pre- and postoperative radiographic morphology. J Am Anim Hosp Assoc 26:73, 1990.

Stone E.A., Mason L.K.: Surgery of ectopic ureters: Types, method of correction, and postoperative results. J Am Anim Hosp Assoc 26:81, 1990.

Samii V.F., McLoughlin M.A., Mattoon J.S., Drost W.T., Chew D.J.: Digital fluoroscopic excretory urography, helical computed tomography and cystoscopy in 24 dogs with suspected ureteral ectopia. J Vet Int Med 2004:18:271-281.

Sutherland-Smith J., Jerram R.M., Walker A. M., Warman C.G.A.: Ectopic ureters and ureteroceles in dogs: presentation, cause and diagnosis. Compend Contin Educ Pract Vet 4:303, 2004.

Sutherland-Smith J., Jerram R.M., Walker A. M., Warman C.G.A.: Ectopic ureters and ureteroceles in dogs: treatment. Compend Contin Educ Pract Vet 4:311, 2004.