Uterus

Introduction

Prepubertal gonadectomy is not a new procedure. Veterinarians in the U.S. have often recommended that female dogs and cats be neutered prior to the first estrus (i.e., prepubertal) to eliminate unwanted pregnancies and reduce the risk of mammary neoplasia. Traditionally, female dogs and cats not intended for breeding purposes have undergone ovariohysterectomy at approximately six months of age. However, in an attempt to help alleviate the pet overpopulation problem, veterinarians began to investigate whether it was also safe to alter puppies and kittens at a younger age.¹ Currently, the literature suggests that prepubertal gonadectomy in female cats is safe as young as 6 to 8 weeks of age, particularly in the shelter environment. In female puppies, however, it is best to delay ovariohysterectomy until at least 3 to 4 months of age to prevent an increased risk of estrogen responsive urinary incontinence.² However, for shelters with an over supply of puppies, the advantages of ovariohysterectomy of puppies before adoption may outweigh the risk of urinary incontinence.

Surgical Anatomy

The surgical anatomy of the pediatric puppy or kitten is identical to that of the adult dog or cat; however, pediatric reproductive tract tissues are extremely small, friable, and susceptible to tearing if not handled with finesse. Additionally, there is minimal fat associated with the broad ligament or ovarian bursa in pediatric puppies and kittens.

Surgical Procedures and Techniques

When performing surgery in the pediatric patient, it is important to remember certain anesthetic and surgical considerations that may differ from the adult animal. Anesthetic and surgical considerations for the pediatric patient include the increased potential for hypoglycemia, hypothermia, a relatively small blood volume, and the delicate nature of pediatric tissues. Since hepatic glycogen stores are minimal in neonates, prolonged fasting may result in hypoglycemia. Food should be withheld no longer than 8 hours, with 3-4 hours recommended for the youngest patients (6-8 weeks).^3,4 Hypothermia can be lessened by using warm water or warm circulating air blankets and by the use of warm intravenous fluids (if used). Minimizing the period under general anesthesia and operative time will also help lessen the severity of hypothermia. Excessive wetting of the pediatric patient during preparation of the surgical site should be avoided, and the use of warmed scrub solution (chlorhexidine) and avoidance of alcohol will be beneficial in helping preserve body heat.^3,4 Pediatric tissues are very friable and should be handled carefully. The relatively small blood volume of pediatric patients makes meticulous hemostasis very important. Fortunately, the small size of blood vessels and the presence of minimal abdominal and ovarian bursal fat allow for excellent visualization of the vasculature, and makes precise hemostasis simple to achieve.

Pediatric ovariohysterectomy may be performed similarly to adult ovariohysterectomy with some slight modifications.^3,5,6 Incisions in puppies are started more caudal to the umbilicus than in adult dogs. Generally, the uterus is more easily exposed in puppies if the incision is started at least 2 to 3 cm caudal to the umbilicus. This results in the incision positioned at, or near, the middle third of the distance from the umbilicus to the cranial brim of the pelvis, similar to an incision made for the adult cat. In kittens, the incision is placed in a similar location as in the adult cat. Upon entrance into the abdomen, it is common to encounter substantial amounts of serous fluid in both puppies and kittens. It may be necessary to remove some of the fluid using gauze sponges to improve visualization. In contrast to adult dogs and cats, it is recommended that the use of a Snook ovariohysterectomy hook be avoided in pediatric patients due to the delicate nature of the uterine tissues. Because of incision location in both puppies and kittens, the uterus is easy to locate by retracting the bladder laterally and looking between the urinary bladder and colon. If necessary, and if incision length will allow, the urinary bladder may be elevated from the abdomen and reflected caudally to permit easier visualization of the uterus. If this technique is used, once the uterus has been identified and secured, the bladder should be returned to the abdomen so as to preserve body heat. Uterine tissues are extremely small and friable in young puppies and kittens, therefore care must be taken to avoid excess traction and tearing of tissues. After the uterus has been located, the suspensory ligament may be carefully broken down to improve exposure and visualization of the ovary. A window is made through the broad ligament adjacent to the ovarian vasculature. A hemostatic clamp is then placed just proximal (medial) to the ovary across the ovarian vessels using a mosquito hemostat on kittens and small puppies and a Kelly, Crile, or Carmalt forceps on larger puppies. Although the triple clamp method may be used in pediatric OHE, it is often cumbersome and difficult to place multiple clamps proximal to the ovary without tearing tissues. The ovarian vessels are doubly ligated using 3-0 to 4-0 absorbable suture material or stainless-steel hemostatic clips. A single ligature may be sufficient to prevent hemorrhaging in very small pedicles, and transfixation ligatures are usually avoided. After ligation and transection of the ovarian vessels on both sides, the remaining broad ligament should be broken down (if it has not already torn) and the uterine pedicle ligated at the junction of the uterine body and cervix with two fully encompassing uterine body ligatures or hemostatic clips. After the reproductive tract has been removed, it should be examined to ensure complete removal (of ovaries and uterine body), and the abdomen should be examined for evidence of hemorrhage. As abdominal wall closure is performed, it is important to carefully identify the ventral fascia (external rectus sheath) and differentiate it from the overlying subcutaneous tissues since they can occasionally be difficult to tell apart (particularly in puppies). The ventral fascia can be closed using either a simple continuous or simple interrupted suture pattern using 3-0 (or possibly 2-0 on large puppies) absorbable (polydioxanone, polyglyconate, or polyglactin 910) suture. The subcuticular layer may be closed with an absorbable suture material (3-0 to 4-0, poliglecaprone 25 preferred) in a continuous intradermal pattern to avoid the use of skin sutures. Alternatively, skin sutures may be loosely placed following closure of the subcutaneous tissues. Although some veterinarians avoid using skin sutures in pediatric patients to prevent premature removal by the patient, we routinely use loosely placed skin sutures without complication or premature removal.

To prevent unnecessary abdominal exploratory surgery in the future, all animals undergoing early age ovariohysterectomy should be tattooed to identify their neutered status. The recommended tattoo site is the prepubic area in females. The female gender symbol along with an encircled “X” is used to denote the neutered status. Tattooing may be performed after the surgical site has been clipped but prior to the surgical prep of the area.

Postoperative Care

Postoperatively, pediatric patients should be monitored for hypoglycemia, hypothermia, pain, or dysphoria. Supplemental heat, glucose containing agents, or additional analgesics or sedatives may be used to ensure smooth recovery from anesthesia. These patients may be fed a small meal one to two hours after recovery since they tend to recover much more quickly from anesthesia and surgery than adults. Unlike traditional age patients undergoing ovariohysterectomy, pediatric puppies and kittens are typically hungry at this time and are often ready to eat and resume normal activity.

Postoperative Complications

Although the anesthetic and surgical procedures for early-age gonadectomy have generally been reported as safe, veterinarians have been concerned about long-term health risks. Veterinarians have questioned whether the immune system of puppies and kittens would be adversely affected by the stress of anesthesia and surgery at early ages and during a time when animals are being immunized against potentially fatal infectious diseases. Veterinarians have also been concerned about the risk of urinary incontinence and neoplasia in female dogs, abnormal long bone growth patterns, and obesity in dogs and cats neutered at an early age. Since the 1990’s, several studies have been published that critically evaluate these concerns among dogs and cats altered at different ages prior to, and following, puberty. These studies, as well as more recent studies, have begun to clarify the long term health risks and benefits of early age ovariohysterectomy as compared to traditional age gonadectomy.

Infectious Diseases and Long-Term Immune Suppression

In some short-term studies conducted at animal shelters, puppies and kittens neutered at early ages had no higher risk of infectious diseases than older animals. One study involved dogs and cats from two animal shelters undergoing gonadectomy surgeries in association with the fourth-year student surgical teaching program of a university teaching hospital.⁵ Twelve of 1988 (0.6%) animals died or were euthanized because of severe infections of the respiratory tract or as the result of parvovirus infection during the 7-day postoperative period, and the deaths (or euthanasias) included similar numbers of animals from all age groups.

In long term studies of 263 cats⁷ (36 month median follow up) and 269 dogs⁸ (48 month median follow up), prepubertal gonadectomy did not result in an increased incidence of infectious diseases after adoption in cats, compared with traditional age gonadectomy. In dogs, however, gonadectomy before 5.5 months of age was associated with increased incidence of parvoviral enteritis. In more recent studies of 1660 cats⁹ (47 month median follow up) and 1842 dogs² (54 month median follow up), those gonadectomized before 5.5 months of age were no more likely than those gonadectomized after 5.5 months of age to have any conditions that might be presumably associated with long term immune suppression. Further, in cats, the study showed that early age gonadectomized cats had a lower incidence of gingivitis, a condition that may be associated with immune suppression. On a short-term basis, however, dogs from the study that were gonadectomized at an early age had an increased incidence of parvoviral enteritis that often occurred soon after adoption. In both of the long-term dog studies^8,2 (269 dogs and 1842 dogs), the increased incidence of parvoviral enteritis on a short-term basis probably represented an increased susceptibility of the younger puppies during the periadoption period, rather than long-term immune suppression.

Body and Long Bone Growth

At one time veterinarians believed that puppies and kittens neutered at an early age might be “stunted” in growth. Several research studies have now defined and dismissed these concerns. In a 15-month study, the effects of prepubertal gonadectomy on skeletal growth, weight gain, food intake, body fat, and secondary sex characteristics were investigated in 32 mixed-breed dogs neutered at seven weeks or seven months or left intact.¹⁰ Growth rates were unaffected by gonadectomy, but the growth period and final radial/ulnar length was extended in bitches neutered at seven weeks of age. Thus, animals were not stunted in growth, but were actually slightly (as determined by radiographs) taller. In a similar study,¹¹ thirty-one cats were neutered at seven weeks or seven months or left intact. Distal radial physeal closure was delayed in gonadectomized cats when compared to intact cats. However, no differences were detected between cats neutered at seven weeks or seven months for mature radius length or time of distal radial physeal closure. Similar findings in cats were reported in another study.¹² In males and females, distal radial physeal closure was delayed in both groups of gonadectomized cats (neutered at seven weeks or seven months of age) compared to intact animals. In female cats, proximal radial physeal closure was also significantly delayed in cats neutered at 7 weeks of age.

The clinical significance of delayed closure of growth plates is not clear, but it does not appear to render the growth plates more susceptible to injury. In the long term studies of 263 cats⁷ and 269 dogs⁸ examining outcome of gonadectomy performed at an early age or traditional age, no differences in the incidence of musculoskeletal problems were seen between groups. Further, in the long term studies of 1660 cats⁹ and 1842 dogs,² age at gonadectomy was not associated with the frequency of long bone fractures. In all these studies, long bone fractures were rare overall, suggesting that physeal fractures are not a common problem in gonadectomized dogs and cats in general.

Long-term studies have examined the incidence of hip dysplasia in dogs and the association with age at gonadectomy. Although one study of 269 dogs⁸ found no association between age at gonadectomy and hip dysplasia, another study of 1842 dogs² found that early age gonadectomy was associated with a significant increased incidence of hip dysplasia. Puppies that underwent gonadectomy before 5.5 months of age had a 6.7% incidence of hip dysplasia, while those that underwent gonadectomy at the more traditional age had an incidence of 4.7%. However, those that were gonadectomized at the traditional age were three times more likely to be euthanized for the condition as compared to the early age group, suggesting that early age gonadectomy may be associated with a less severe form of hip dysplasia. A recent study showed that in the Golden Retriever breed, cranial cruciate ligament rupture was seen more frequently in dogs neutered before 1 year of age (early neutered) than those neutered after a year of age or remaining intact.¹⁷ Although the incidence of hip dysplasia was higher in males of the early neutered group as compared to the intact group, this was not the case in the female dogs.

Obesity

Although obesity can occur in both neutered and intact animals, and is influenced by a number of factors such as diet and activity level, there are data to suggest that neutered cats may gain significantly more than those remaining intact. Clinically, spayed females seem likely to gain weight however objective data concerning whether dogs are more likely to experience weight gain following ovariohysterectomy is less clear. When comparing gonadectomized cats to sexually intact cats, intact cats were found to weigh less than cats altered at seven months, but there was no difference between intact cats and those neutered at seven weeks.¹¹ Another study,¹² 13 of 34 cats assessed obesity by body mass index at 24 months of age. Body condition scores and body mass index values were higher in animals gonadectomized at seven weeks or seven months than in intact animals, indicating that animals gonadectomized at either age were more likely to be obese than intact cats. Heat coefficient, a measure of resting metabolic rate, was higher in intact cats than in gonadectomized cats. Based on these data, the author suggested that neutered female cats require an intake of 33% fewer calories than intact female cats.¹³ Another study¹⁴ confirmed these findings, and demonstrated that the maintenance energy requirement is substantially lower for spayed female cats than for sexually intact cats. It was noted that sexually intact cats appeared to self regulate food intake, whereas spayed cats tended to eat all food available.

Information on body condition was gathered on over 8000 dogs from 11 veterinary practices in the United Kingdom during a six month survey.¹⁵ In this retrospective study, spayed dogs were about twice as likely to be obese as intact female dogs. However, another study¹⁰ found no differences in food intake, weight gains, or back-fat depth among neutered (seven weeks or seven months) and intact animals during a 15-month prospective study. Interestingly, a long-term study of 1842 dogs² actually found that the proportion of overweight dogs was lowest in the early age gonadectomized dogs, as compared to the traditional age dogs.

Estrogen Responsive Urinary Incontinence

The incidence of estrogen-responsive urinary incontinence is increased among neutered female dogs and there is concern that gonadectomizing puppies at an earlier age might further increase the risk for spayed bitches. Urinary incontinence in dogs neutered at traditional ages can develop within days of the surgery or not until several years later. Estrogen-responsive urinary incontinence was reported in 34 of 791 (4%) bitches neutered at traditional ages, and seven of 2,434 (0.3%) sexually intact bitches.¹⁶ A long term study that evaluated 269 dogs⁸ adopted from shelters and neutered before 5.5 months of age, or ≥ 5.5 months of age, found only three cases where owners reported urinary incontinence. One dog was neutered at an early age and two dogs were neutered at the traditional age. In contrast, however, the long term study of 1842 dogs² demonstrated that decreasing age at the time of ovariohysterectomy was associated with increasing incidence of urinary incontinence that required medical treatment. Puppies that underwent ovariohysterectomy before three months of age appeared to be at the greatest risk. Based upon this study, female puppies should not undergo ovariohysterectomy until at least three to four months of age. The authors note, however, that in certain shelter environments, the need for gonadectomy prior to adoption may outweigh the risk of urinary incontinence.

Perivulvar Dermatitis

The vulvas of puppies neutered prior to puberty appear smaller when compared to intact bitches. Vulvar size may also appear small in intact bitches during anestrus or in some bitches spayed later in life. Perivulvar dermatitis can result in bitches with recessed or small vulvas, especially if the bitch has excessive skin and adipose tissue that cause skin folds that partially cover the vulva. Although perivulvar dermatitis has been associated with weight gains and recessed vulvas following ovariohysterectomy, there is no data to suggest that the occurrence is higher in bitches spayed at early ages over those neutered at conventional ages.

Neoplasia

Compared to intact dogs, gonadectomized dogs have been reported to have a higher risk of osteosarcoma, despite the fact that the neutered dogs actually lived longer than the intact dogs.^18,19

Additionally, it has been suggested that ovariectomized females may be at an increased risk of hemangiosarcoma when compared to intact females,^20,21 although this was not confirmed in a later study.¹⁷ Although rare, transitional cell carcinoma of the bladder may be seen more frequently in neutered dogs than in intact dogs.²²

References

1. Lieberman, LL: A case for neutering pups and kittens at two months of age. J Am Vet Med Assoc 191:518, 1987.
2. Spain, CV, Scarlett JM, Houpt KA: Long-term risks and benefits of early-age gonadectomy in dogs. J Am Vet Med Assoc 224:380, 2004.
3. Faggella AM, Aronsohn MG: Evaluation of anesthetic protocols for neutering 6- to 14-week-old pups. J Am Vet Med Assoc 205:308, 1994.
4. Faggella AM, Aronsohn MG: Anesthetic techniques for neutering 6- to 14-week-old kittens. J Am Vet Med Assoc 202:56, 1993.
5. Howe LM: Short-term results and complications of prepubertal gonadectomy in cats and dogs. J Am Vet Med Assoc 211(1):57, 1997.
6. Aronsohn MG, Faggella AM: Surgical techniques for neutering 6- to 14-week-old kittens. J Am Vet Med Assoc 202:53, 1993.
7. Howe LM, Slater MR, Boothe HW, et al.: Long-term outcome of gonadectomy performed at an early age or traditional age in cats. J Am Vet Med Assoc 217:1661, 2000.
8. Howe LM, Slater MR, Boothe HW, et al.: Long-term outcome of gonad- ectomy performed at an early age or traditional age in dogs. J Am Vet Med Assoc 218:217, 2001.
9. Spain CV, Scarlett JM, Houpt KA: Long-term risks and benefits of early-age gonadectomy in cats. J Am Vet Med Assoc 224:372, 2004.
10. Salmeri KR, Bloomberg MS, Scruggs SL, et al.: Gonadectomy in immature dogs: Effects on skeletal, physical, and behavioral development. J Am Vet Med Assoc 198:1193, 1991.
11. Stubbs WP, Bloomberg MS, Scruggs SL, et al.: Prepubertal gonadectomy in the domestic feline: Effects on physical and behavioral development. J Am Vet Med Assoc 209: 1864, 1996.
12. Root MV: The effect of prepubertal and postpuberal gonadectomy on the general health and development of obesity in the male and female domestic cat. PhD Thesis, University of Minnesota, Saint Paul, MN, 1995.
13. Root MV: Early spay-neuter in the cat: effect on development of obesity and metabolic rate, Veterinary Clinical Nutrition 2:132, 1995.
14. Flynn MF, Hardie EM, Armstrong J: Effects of ovariohysterectomy on maintenance energy requirements in cats. J Am Vet Med Assoc 209:1572, 1996.
15. Edney ATB and Smith PM: Study of obesity in dogs visiting veterinary practices in the United Kingdom. Vet Rec 118:391, 1986.
16. Thrusfield MV: Association between urinary incontinence and spaying in bitches. Vet Rec 116:695, 1985.
17. De la Riva GT, Hart BL, Farver TB, et al.: Neutering dogs: effects on joint disorders and cancers in Golden Retrievers. PLOS One 8(2):e55937, 2013.
18. Cooley DM, Beranek BC, Schlittler DL, et al.: Endogenous gonadal hormone exposure and bone sarcoma risk. Cancer Epidemiol Biomarkers Prev 11(11):1434-1440, 2002.
19. Ru G, Terracini B, Glickman LT: Host related risk factors for canine osteosarcoma. Vet J 156(1):31-39, 1998.
20. Ware WA, Hopper DL: Cardiac tumors in dogs: 1982-1995. J Vet Intern Med 13(2):95-103, 1999.
21. Prymak C, McKee LJ, Goldschmidt MH, et al.: Epidemiologic, clinical, pathologic, and prognostic characteristics of splenic hemangiosarcoma and splenic hematoma in dogs: 217 cases (1985). J Am Vet Med Assoc 193(6):706-712, 1988.
22. Norris AM, Laing EJ, Valli VE, et al.: Canine bladder and urethral tumors: a retrospective of 115 cases (1980-1985). J Vet Intern Med 6(3):145-153, 1992.
     

Indications

The most common indication for ovariohysterectomy (OVH) is elective sterilization. Ovariohysterectomy is the treatment of choice for most uterine diseases including pyometra, uterine torsion, localized or diffuse cystic endometrial hyperplasia, uterine rupture, and uterine neoplasia.¹ In a study of 1712 ovariohysterectomies in dogs, 82% were performed for elective sterilization, 18% for reproductive tract disease, and 7% as adjunctive therapy for mammary neoplasia.² Ovariohysterectomy is indicated for diabetic and epileptic animals to prevent hormonal changes that alter the effectiveness of medications.

Endogenous estrogen production plays a role in the etiology of spontaneous mammary tumors.³ Ovariohysterectomy before the first estrus provides a definitive protective factor, reducing the incidence of mammary neoplasia to 0.5%.^1,3 The risk factor is 8% when ovariohysterectomy is delayed until after one estrus, and after two or more estrus cycles, the risk rises to 26%.^1,3

Ovariohysterectomy may be a justifiable adjuvant therapy for mammary neoplasia. Controversy exists, however OVH may inhibit the recurrence of benign or malignant tumors that have estrogen receptors. Proponents of OVH also note that remaining mammary tissue atrophies permitting easier surgery on any mammary tumors that subsequently develop.

Surgical Anatomy

The ovaries, oviducts, and uterus are attached to the dorsolateral walls of the abdominal cavity and the lateral wall of the pelvic cavity by paired double folds of peritoneum called the right and left broad ligaments. Cranially, the broad ligament is attached by means of the suspensory ligament of the ovary (Figure 33-1). The broad ligament is divided into three regions: the mesovarium, the mesosalpinx, and the mesometrium. The suspensory ligament runs from the ventral aspect of the ovary and mesosalpinx cranially and dorsally to the middle and ventral thirds of the last two ribs.³ The proper ligament is the caudal continuation of the suspensory ligament. The proper ligament attaches to the cranial end of the uterine horn. The round ligament of the uterus attaches to the cranial tip of the uterine horn and is a caudal continuation of the proper ligament. The round ligament extends caudally and ventrally in the broad ligament, and, in most bitches, it passes through the inguinal canal and terminates subcutaneously near the vulva.⁴

The ovarian arteriovenous (AV) complex lies on the medial side of the broad ligament and extends from the aorta to the ovary. The distal two-thirds of the ovarian AV complex is convoluted, similar to the pampiniform plexus in males.² The ovarian artery is less convoluted in cats.⁵ The ovarian artery supplies the ovary and the cranial portion of the uterine tube in the dog and cat. The arterial supply to the uterus in the nonpregnant dog and cat is relatively independent of the supply to the ovary. Small anastomoses in the broad ligament are present between branches of the ovarian artery and branches of the uterine artery.⁵
 

The left ovarian vein drains into the left renal vein, and the right ovarian vein drains into the caudal vena cava. The uterine veins run in close association with the uterine arteries and terminate caudally into the internal iliac veins.

Surgical Technique

The urinary bladder should be manually expressed before ovariohysterectomy. A midline abdominal incision is made extending from the umbilicus to a point halfway between the umbilicus and the brim of the pubis in the dog. The incision begins approximately 1cm caudal to the umbilicus in the cat and extends approximately 3 to 5 cm caudally. The abdominal incision must be carried further caudally in the cat to provide adequate exposure of the uterine body. A longer abdominal incision is recommended if the uterus is enlarged. The left or right uterine horn is located by using either an ovariohysterectomy (Snook) hook or the surgeon’s index finger. A small hemostat may be placed on the proper ligament to aid in retraction of the ovary. The suspensory ligament is stretched or broken using the index finger (Figure 33-2A). Tension must be directed caudally along the dorsal body wall rather than perpendicular to the incision to avoid tearing the ovarian AV complex. Separate ligation of the suspensory ligament is seldom necessary. The ovarian AV complex is located, and a “window” is made in the mesovarium immediately caudal to the complex (Figure 33-2B). The ovarian AV complex is double clamped using Rochester-Carmalt hemostatic forceps in the canine or mosquito hemostats in the feline (Figure 33-3). The surgeon should maintain constant digital contact with the ovary when applying the first clamp to ensure that the entire ovary is removed. A third clamp is placed over the proper ligament between the ovary and uterine horn (Figure 33-4). The pedicle is severed between the middle clamp and the ovary (Figure 33-4). When this technique is used, the pedicle is severed between the middle clamp and the clamp closest to the ovary (See Figure 33-4, inset). Clamps should be placed on the ovarian pedicle as close to the ovary as possible to prevent accidental inclusion of the ureter.
 

Absorbable suture (e.g., chromic catgut, polydioxanone, or polyglyconate) is preferred for all ligatures. A circumferential suture is loosely placed around the proximal clamp (Figure 33-5). The clamp is removed while the circumferential suture is tightened so the circumferential suture lies in the groove of crushed tissue created by the clamp (Figure 33-5, inset). As the suture is tightened the second hemostatic clamp is “flashed” or temporarily opened which allows the tissue pedicle to return to its circumferential configuration and allows complete tightening of the first ligature. The benefits of clamp “flashing” are more noticeable in larger tissue pedicles. A second circumferential or transfixation suture is placed between the first circumferential suture and the cut end of the pedicle (Figure 33-6). The pedicle is grasped (without grasping the ligature) with thumb forceps, the final clamp is released, and the pedicle is inspected for bleeding. If no bleeding occurs, the pedicle is replaced into the abdomen.

The ipsilateral uterine horn is isolated by following the first side uterine horn distally to the bifurcation. The ligation procedure is repeated on the right ovarian pedicle. A window is made in the broad ligament adjacent to the uterine artery and vein (Figure 33-7A). The broad ligament is grasped and torn (Figure 33-7B and C). Mass ligation of the broad and round ligament is seldom necessary; however, large vessels in the broad ligament should be ligated especially in larger mature dogs.
 

The uterine body is exteriorized, and the cervix is located. Various techniques may be used to ligate and divide the uterine body, depending on the size of the uterus and the surgeon’s preference. The triple-clamp technique may be used when the uterine body is small, such as in cats and small dogs. Three clamps are placed immediately proximal to the cervix. Care must be taken when applying clamps to the uterine body particularly in the cat because the clamps may cut rather than crush the tissue. Some surgeons prefer to not use crushing clamps on the feline uterine body. The uterine body is severed between the middle clamp and the proximal clamp. The uterine arteries and veins are individually ligated between the distal clamp and the cervix. A circumferential suture is loosely placed around the distal clamp, the clamp is removed, and the suture is tightened in the groove of crushed tissue. A transfixation suture is placed between the circumferential suture and the remaining clamp. The remaining clamp is removed, and the uterine stump is evaluated for bleeding and replaced into the abdomen.

A second technique for ligation of the uterine body involves placement of bilateral individual ligatures on each uterine artery. The uterine body is exteriorized and retroflexed. Sutures that initially incorporate the uterine artery and vein and a small bite of uterine serosa are placed on either side of the uterine body (Figure 33-8A and B). A clamp may be loosely placed proximal to the sutures to prevent backflow of blood after transection. The uterine body is severed between the clamp and the proximal sutures (Figure 33-8C). The uterine stump is evaluated for bleeding and is replaced into the abdomen. This technique is advantageous because clamps are not placed on the section of the uterine body that is ligated; therefore, the potential for cutting the tissue with the clamp is eliminated. Depending on the size of the uterine body and vessels, either mass ligatures, transfixation, or individual ligatures may be used to safely ligate the uterine vasculature.
 

A Parker-Kerr suture pattern has been used for ligation when the uterine body is greatly enlarged (i.e.-pyometra) but is seldom if ever indicated. A Parker-Kerr pattern has the potential for creating a closed cavity of tissue thus preventing drainage of infected material. The uterine arteries and veins should be ligated separately distal to the Parker-Kerr suture pattern.

The ovarian pedicles and uterine stump should be evaluated for bleeding before abdominal closure. The left ovarian pedicle is located by retracting the descending colon medially to expose the left paralumbar fossa. Retraction of the descending duodenum medially exposes the right paralumbar fossa and the right ovarian pedicle. The ovarian pedicles lie immediately caudal to the caudal pole of the kidneys. The uterine stump lies between the bladder and colon and is located by retroflexing the bladder. Sutures should not be grasped when evaluating the ovarian pedicles and uterine stump because excessive traction on the suture may cause it to loosen.

The abdominal incision is closed with either a simple interrupted or simple continuous suture pattern using appropriately sized polydioxanone suture. Sutures should be placed in the external rectus sheath.⁶ It is not necessary to suture the internal rectus sheath or the peritoneum.⁶ The subcutaneous tissue and skin are closed routinely.

A flank approach for feline ovariohysterectomy is used widely in Europe, but it is not recommended. Recovery of a dropped ovarian pedicle is problematic, and it may be difficult to expose the opposite ovary and the uterine bifurcation through this approach.⁷

Complications and Sequelae

Hemorrhage

Intra-operative hemorrhage has been reported as the most common complication of ovariohysterectomy in dogs over 25 kg.⁸ Hemorrhage during ovariohysterectomy may result from tearing of the ovarian AV complex while strumming the suspensory ligament. This complication may be avoided by carefully strumming the ligament as previously described. Intra-operative hemorrhage also may result from tearing of large vessels in the broad ligament, tearing of the uterine vessels by excessive traction on the uterine body, or accidental releasing of a clamp before placement of ligatures. Large vessels in the broad ligament should be individually ligated, and excessive traction on the uterine body should be avoided by lengthening the abdominal incision.¹ Improperly placed sutures may result in intra-operative or post-operative hemorrhage. The ovarian pedicles and uterine stump should be double ligated and evaluated for bleeding before abdominal closure. Other potential sources of hemorrhage that may be noted intra-operatively include the abdominal musculature, (rectus abdominis muscle), subcutaneous tissue and skin. 

Uterine Stump Pyometra

Uterine stump pyometra can occur if the animal has elevated blood progesaterone levels. The source of progesterone may be endogenous, from residual ovarian tissue (incomplete removal), or exogenous, from progestational compounds used to treat dermatitis.^1,9 Uterine stump pyometra can be prevented by ensuring complete removal of the ovaries during OVH.

Recurrent Estrus (Ovarian Remnant Syndrome)

Recurrent estrus usually results from functional residual ovarian tissue after incomplete ovariohysterectomy. Clinical signs associated with estrus and ovarian hormonal activity may be present.¹⁰ The hormonal effects may be delayed, depending on whether or not vascularity to the ovarian remnant has been maintained. Collateral circulation to the ovarian tissue may develop even though the ovarian AV complex has been ligated and transected.¹¹ Treatment of recurrent estrus after ovariohysterectomy is surgical exploration and excision of residual ovarian tissue. Surgical exploration during estrus is preferable. Identification of an ovarian remnant on one side should not preclude inspection of the other ovarian site.¹⁰ Functional residual ovarian tissue is more commonly found on the right side.¹² Residual ovarian tissue occasionally cannot be identified or palpated, and its presence is often made manifest by increased vascularity of the ovarian pedicle. All excised tissue should be submitted for histopathologic examination. A disproportionate number of cats that develop the ovarian remnant syndrome have been operated through a flank incision.¹⁰ Incomplete ovariectomy may be prevented by maintaining constant digital contact with the ovary during application of hemostatic clamps to the ovarian AV complex.

Ligation of Ureter

Accidental ligation of a ureter may occur during ligation of the uterine body or an ovarian AV complex.¹² Ligation of a ureter results in hydronephrosis and may predispose to pyelonephritis. The ureter may be accidentally crushed or ligated if the ovarian AV complex is dropped and indiscriminate clamping of tissue occurs in the lumber gutter. A ureter is more likely to be included in a uterine body ligature if the bladder is full because the trigone and vesicoureteral junction are cranially displaced, resulting in more slack on the ureters. Accidental ligation or crushing of a ureter may be prevented by ligating the ovarian AV complex as close to the ovary as possible, by evacuating the patient’s urinary bladder preoperatively, and by isolating and ligating the uterine vessels carefully.

Urinary Incontinence

Urinary incontinence after ovariohysterectomy can be caused by a low systemic estrogen level, by adhesions or granulomas of the uterine stump that interfere with urinary bladder sphincter function, or by vaginoureteral fistulation from common ligation of the vagina and ureter.¹³ Estrogen-responsive urinary incontinence may occur in any spayed bitch and is a poorly understood sequela of ovariohysterectomy.¹⁴ The onset of estrogen responsive incontinence postoperatively is variable and may take several years.¹⁴ The mean reported age of onset is 8.3 years and bitches spayed before 12 weeks of age appear to be at increased risk for developing incontinence.¹⁴ The recommended therapy for estrogen-responsive urinary incontinence is oral administration of phenylpropanolamine (1.5-2.0 mg/kg PO, bid to tid) or diethylstilbestrol at 0.1 to 1.0 mg per day for 3 to 5 days, followed by a maintenance does of 1.0 mg per week.¹⁴

Fistulous Tracts and Granulomas

The most common cause of sublumbar fistulous tracts in spayed bitches is adverse tissue reaction to implanted nonabsorbable multifilament suture material (e.g., polymerized caprolactam, Braunamid, B. Braun Melsurgen AG, Germany) used for ovarian or uterine ligature.^12,15-17 The high bacterial adherence and capillarity of multifilament suture may contribute to persistent and progressive infection when the suture is contaminated with bacterial organisms and is buried in tissue.¹⁸ No ovarian or uterine stump granulomas or fistulous tracts were reported in 377 bitches that had ovariohysterectomies using 2-0 chromic catgut suture.⁸

The interval between ovariohysterectomy and appearance of fistulous tracts is often several months and may be several years.¹² Fistulous tracts can occur anywhere on the trunk, although they most commonly occur in the flank when associated with ovarian pedicle ligatures and in the inguinal or thigh region when associated with a uterine ligature.¹⁸ Ovarian pedicle granulomas caused by adverse tissue reaction to suture material may involve the kidney or proximal ureter, resulting in hydronephrosis and pyelonephritis. Uterine stump granulomas may involve the urinary bladder, distal ureters, or colon, leading to cystitis, pollakiuria, urinary incontinence, or bowel obstruction.¹⁸ Exploratory celiotomy with excision of the offending ligature and of associated granulation tissue is the treatment of choice. All ovarian and uterine ligatures should be removed even though some appear uninvolved because they may subsequently provoke an adverse tissue response.¹² Local exploration of fistulous tracts is seldom successful and is indicated only if exploratory celiotomy fails to identify the offending tissue.¹ The use of absorbable suture material for ovarian and uterine ligatures during ovariohysterectomy reduces or removes the incidence of this complication.¹⁸

Body Weight Gain

Body weight gain was the most common long-term sequela reported in one study, occurring in 26.2% of bitches undergoing elective ovariohysterectomy.¹⁹

The cause of excessive weight gain after ovariohysterectomy is poorly understood. One theory suggests that the fat deposits of the body possess receptors for specific steroid hormones so deposition is blocked or facilitated in a regional manner in response to testosterone, estradiol, progesterone, and cortisol. Estradiol inhibits lipoprotein lipase in adipocytes of fat deposits, so circulating fatty acides cannot be esterified and deposited.²⁰ A low systemic estradiol level after ovariohysterectomy may lead to excessive fat deposition and weight gain.

Eunuchoid Syndromes

The eunuchoid syndrome is occasionally observed in working dogs after ovariohysterectomy. Affected dogs have decreases in aggression, interest in work, and stamina.²⁰ Autotransplantation of an ovary to the subserosa of the stomach wall, which is drained exclusively by the portal vein, may prevent this complication.²⁰ The graft produces estradiol and progesterone, which are partially metabolized by the liver. Circulating estradiol levels are inadequate to initiate estrus, but they are sufficient to prevent the eunuchoid syndrome.²⁰

Complications of Celiotomy

Accidental incision of the spleen or urinary bladder, failure to remove all gauze sponges from the abdominal cavity before closure, dehiscence, seroma formation, and self-mutilation may occur with any abdominal procedure. Self-inflicted trauma of the abdominal wound is the most commonly reported complication of ovariohysterectomy of dogs less than 25 kg.⁸ Most of these complications can be prevented by gentle tissue handling, close attention to surgical detail and by adhering to the basic principles of aseptic surgical technique.

Early Prepubertal Gonadectomy

Minimal scientific evidence exists to support the widely accepted practice of delaying elective sterilization until an animal is 5 to 8 months old. Veterinarians are comfortable with this practice because untoward effects occur infrequently. Early prepubertal gonadectomy (i.e., at 8 to 12 weeks of age) has been investigated because the efficacy of sterilization programs could be enhanced if all animals were neutered before adoption. Much has been learned about the effects of early prepubertal gonadectomy on skeletal growth, obesity, behavior, secondary sex characteristics, anesthetic risk, and immunology.²¹ The current body of knowledge supports the notion that early prepubertal gonadectomy is not deleterious²¹ (See Chapter 35).

References

1. Stone EA. Ovariohysterectomy. In: Slatter DC, ed. Textbook of small animal surgery. Philadelphia: WB Saunders, 1985:1667-1672.
2. Wilson GP, Hayes HM. Ovariohysterectomy in the dog and cat. In: Bojrab MJ, ed. Current techniques in small animal surgery. 2nd ed. Philadelphia: Lea & Febiger, 1983:334-338.
3. Farton JW, Withrow SJ. Canine mammary neoplasia: an overview. Calif Vet 1981;7;12.
4. Evans HE, Christensen GC. Miller’s anatomy of the dog. 2nd ed. Philadelphia: WB Saunders, 1981.
5. DelCampo CH, Ginther OJ. Arteries and veins of uterus and ovaries in dogs and cats. Am J Vet Es 1974;35:409.
6. Rosin E. Single layer, simple continuous suture pattern for closure of abdominal incisions. J Am Anim Hosp Assoc 1985;21:751.
7. Krzaczynski J. The flank approach to feline ovariohysterectomy. Vet Med Small Anim Clin 1974;May :572.
8. Berzon JL. Complications of elective ovariohysterectomies in the dog and cat at a teaching institution: a clinical review of 853 cases. Vet Surg 1978;8:89.
9. Teale ML. Pyometritis in spayed cats (letter). Vet Rec 1972;90:129.
10. Stein BS. The genital system. In: Catcott EJ, ed. Feline medicine and surgery. 2nd ed. Santa Barbara, CA: American Veterinary, 1975.
11. Shenwell RE, Weed IC. Ovarian remnant syndrome. Obstet Gynecol 1970;36:299.
12. Pearson H. The complications of ovariohysterectomy in the bitch. J Small Anim Pract 1973;14:257.
13. Pearson H. Gibbs G. Urinary incontinence in the dog due to accidental vaginoureteral fistulation during hysterectomy. J Small Anim Pract 1980;21:287.
14. Rosin AH, Ross L. Diagnosis and pharmacological management of disorders of urinary continence in the dog. Compend Contin Educ Pract Vet 1981;3:601.
15. Osborne CA, Polzin DJ. Canine estrogen responsive incontinence: an enigma. DVM .
16. Pearson H. Ovariohysterectomy in the bitch. Vet Rec 1970; 87:257.
17. Borthwick R. Unilateral hydronephrosis in a spayede bitch. Vet Rec 1972;90:244.
18. Spackmann CJ, Caywood DD, Johnston GB, et al. Granulomas of the uterine and ovarian stumps: a case report. J Am Anim Hosp Assoc 1948;20:449.
19. Dorn AS, Swist RA. Complications of canine ovariohysterectomy. J Am Anim Hosp Assoc 1977;13:720.
20. LeRoux PH, Van Der Walt LA. Ovarian autograft as an alternative to ovariectomy in bitches. J S Afr Vet Med Assoc 1977; 48:117.
21. Salmeri KR, Olson PN, Bloomberg MS. Elective gonadectomy in dogs: a review. J Am Vet Med Assoc 1991;198:1183.
     

Introduction

Ovariohysterectomy (OVH) is the most common elective surgical procedure performed for small animal sterilization in the United States.¹ Ovariohysterectomy provides canine and feline population control and decreases the incidence of life threatening diseases such as pyometra and mammary cancer. It is well documented that traditional OVH procedures performed by celiotomy inflict pain and morbidity in veterinary patients as a result of tissue trauma, organ manipulation, and inflammation.^2,3 With an increasing concern for postoperative morbidity from owners and increased public awareness of minimally invasive techniques, the frequency of minimally invasive veterinary procedures has increased recently.

Preoperative Considerations

Advantages and Disadvantages

Laparoscopic ovariohysterectomy and hysterectomy procedures in human and veterinary patients have been shown to have numerous advantages over traditional celiotomy techniques including decreased postoperative stress and pain, faster recovery periods, decreased hospital stays, improved cosmesis, and improved visualization of abdominal organs.⁴ Two recent veterinary studies documented decreased postoperative pain and less incisional erythema in laparoscopic ovariohysterectomy patients.^5,6 Disadvantages of laparoscopic ovariohysterectomy include the inherent limitations of minimally invasive surgery, cost of equipment, procedural learning curve, and increased time of the operative procedure compared to traditional surgical techniques.

Anesthesia

The anesthetist should be prepared for changes in the cardiovascular and pulmonary systems during surgery. After induction of general anesthesia and aseptic preparation of the abdomen for surgery the animal is placed in a modified Trendelenburg position which requires a 20 to 30° tilt in the surgical table, placing the pelvic limbs above the level of the head.⁷ This positioning provides the surgeon with better visualization of the caudal abdominal organs. However, this patient position can lead to increased pressure on the diaphragm from viscera leading to cardiopulmonary dysfunction. In addition, laparoscopic surgery requires insufflation of the abdomen with gas which increases abdominal pressure. Intra-abdominal pressures above 15 mm Hg can lead to decreased venous return and cardiac output, vasovagal reflexes, decreased compliance of the diaphragm, and ventilationperfusion mismatch.^4,8,9 Finally, although the risk of gas embolus is low, due to carbon dioxide’s high blood solubility, fluctuation in cardiopulmonary system function should be monitored carefully.

Harmonic Scalpel

The harmonic scalpel consists of an electrical generator, handpiece, an active and inactive blade system, and a foot pedal. Electrical energy is produced through an external generator and converted to ultrasonic energy by means of a piezoelectric, ceramic transducer located within the handpiece. The piezo-electric crystal vibrates at approximately 55,000 hertz, causing longitudinal movement against the inactive part of the blade. Mechanical energy from the oscillating blades results in energy transfer to tissue proteins, leading to protein denaturization and the formation of a sticky protein coagulum. This protein coagulum is capable of sealing vessels as large as 5 mm in size.^11,12

The harmonic scalpel has been used for safe hemostasis in hysterectomy and other abdominal procedures for humans and ovariohysterectomy procedures in horses and dogs. The harmonic scalpel was designed to be used through laparoscopic and thorascopic instrument portals. This scalpel is able to cut, coagulate, and seal vessels simultaneously at much lower temperatures (50 to 100°C) than electrosurgery or laser surgical devices (150 to 400°C).^5,10 The ability to seal vessels at low temperatures with a protein coagulum is referred to as coaptive coagulation. Because of the lower temperatures, less collateral tissue damage occurs with the harmonic scalpel when compared to monopolar and bipolar cautery. In addition, the risk of stray electricity and electrical burn is eliminated with the harmonic scalpel. Lasers and cautery units vaporize cells via rapid heating and cellular explosion, resulting in eschar and smoke formation. Smoke from these devices can accumulate and decrease visualization in a hollow cavity and slow operative time. The harmonic scalpel produces no smoke, thus allowing rapid coagulation with excellent visualization of the surgical field.

Surgical Procedure

The ventral abdomen is prepared for surgery by wide clipping from the xiphoid to the pubis. Following routine preparation of the abdomen for surgery four quarter drapes are placed approximately 2 cm lateral to each row of mammary teats, at the level of the xiphoid cranially, and at the level of the pubis caudally. The dog is then placed in a Trendelenburg position to facilitate craniad displacement of the visceral contents. A 1 cm skin incision is made at the level of the umbilicus to expose the linea alba.

The abdomen is entered through the linea alba with a surgical trocar (Endopath^® 355S Surgical Trocar Ethicon Endo-Surgery, Cincinnati OH) using the Hasson technique. Pneumoperitoneum is established with an insufflator (Electronic Insufflator Model 26012, Karl Storz,) to a pressure of 10mmHg using carbon dioxide gas. A 30° forward-oblique, 5 mm telescope (Hopkins II, Karl Storz, Charleston, MA) is placed through the umbilical port and used to identify the epigastric blood vessels in the abdominal wall to facilitate placement of the paramedian instrument ports under direct camera supervision (5X Hunt Trocar / 5 mm Pyramidal Tip, Apple Medical Corp, Bolton, MA). Each port is introduced 1cm lateral to the 4th mammary teat in the caudal abdomen, using care to avoid the caudal superficial epigastric artery and vein. (Figure 33-9) Babcock forceps (Endopath—5 mm Babcock Forceps, Ethicon Endo-Surgery Inc, Cincinnati, OH) are then placed through the right paramedian portal and clamped to the proper ligament of the right ovary. Caudo-ventral tension is maintained on the ovarian vascular pedicle and suspensory ligament using the Babcock forceps. The harmonic scalpel (Ultracision LCSC5, Ethicon Endo-Surgery Inc, Cincinnati, OH) should then be placed through the left paramedian port and the suspensory ligament, ovarian vascular pedicle, and broad ligament of the uterus are transected and coagulated from cranial to caudal to the level of the uterine body. The uterine artery and vein are transected just proximal to the cervix, followed by the body of the uterus. The procedure is then repeated in reverse order on the left side transecting the broad ligament of the uterus first, followed by the left suspensory ligament, and finally the ovarian pedicle.
 

All of the transected areas are inspected for hemorrhage after completion of the procedure. The camera is then removed from the umbilical port and placed into the instrument port. Babcock forceps are then introduced through the umbilical port, clamped to the uterine body, and the entire reproductive tract is withdrawn through the umbilical port under direct camera visualization.

Pressure is applied to each side of the abdominal wall to facilitate the escape of carbon dioxide gas from the abdominal cavity prior to closure. The umbilical port can be closed with one, simple interrupted, absorbable suture. The subcutaneous tissue of the umbilical port is apposed with one, simple interrupted, absorbable, cruciate suture, followed by a single simple interrupted cruciate, nonabsorbable, skin suture. The paramedian ports are apposed similarly.

Alternative to Use of the Harmonic Scalpel

If a harmonic scalpel is not available or not used; other extracorporeal or intracorporeal knot tying techniques including Endoloop and Endoknot sutures can be placed on the ovarian and uterine pedicles for hemostasis. The Endoloop sutures consist of a pretied Westin Knot. These loops are placed through the ipsilateral cannula to the level of the intended tissue to be ligated and the loop is slowly closed with a knot pusher. The major disadvantage of using intracoporeal and extracorporeal sutures are the increased operative time and learning curve associated with their use, as well as, the risk of continued hemorrhage at the ovarian and uterine pedicles.^6,13

Bipolar and monopolar laparoscopic cautery units can also be used for coagulation of ovarian and uterine pedicles. However, visualization during laparoscopy can be impaired by smoke when using bipolar cautery units within the abdomen. These affects are more profound in smaller sized animals. Also, when using any cautery unit there is a risk of collateral thermal damage, due to much higher coagulation temperatures and stray electricity to surrounding organs. One study evaluated laparoscopic ovariectomy using monopolar and bipolar cautery techniques. There was mesovarial arterial bleeding in 8% of dogs treated with bipolar cautery and 13% of dogs where monopolar cautery was used. Additional Endoloop ligatures were required to prevent recurrent hemorrhage in 20 of 103 of the reported cases.¹⁴ The harmonic scalpel produces no smoke and minimal vapor. No additional hemostasis was required in any dog in one study where the harmonic scalpel was used.⁵

The use of the harmonic scalpel technique could be used for ovariectomy, as well as ovariohysterectomy procedures. Surgical times for ovariohysterectomy procedures with HALO are consistently less than 1 hour in duration and have been shown to decrease postoperative pain when compared to traditional OVH celiotomy techniques. With experience and proper training the HALO procedure provides a safe, efficient, minimally invasive technique for a commonly performed elective surgery. Laparoscopic OVH will likely become more common as owners and veterinarians seek less invasive surgical procedures for animals.

Editor’s Note: The use of the harmonic scalpel and energy vessel sealing devices are well established in minimally invasive surgery (MIS). Several techniques of performing MIS ovariectomy or ovariohysterectomy are successfully used in the bitch.

References

1. Stone EA, Cantrell CG, Sharp NJ: Ovary and Uterus, in Slatter D (ed): Textbook of Small Animal Surgery (ed 2). Philadelphia, W.B. Saunders, 1993, pp 1293-1308.
2. Hardie EM, Hansen BD, Carrol GS: Behavior after ovariohysterectomy in the dog: what’s normal. Applied Animal Behvior Science 51:111-128, 1997.
3. Slingsby LS, Lane EC, Mears ER, et al: Postoperative pain after ovario- hysterectomy in the cat: a comparison of two anesthetic regimens. Vet Rec 143:589-590, 1998.
4. Remedios AM, Fergusen J: Minimally Invasive Surgery: Laparoscopy and thoracoscopy in small animals. Compendium of Continuing Education 18:51-57, 1996.
5. Hancock R, Lanz OI, Waldron DR, et al: Comparison of Postoperative Pain after Ovariohysterectomy By Harmonic Scalpel-Assisted Laparoscopy Compared With Median Celiotomy and Ligation In Dogs. Vet Surg 34:1-10, 2005.
6. Davidson EB, Moll DH, Payton ME: Comparison of Laparoscopic Ovariohysterectomy and Ovariohysterectomy in Dogs. Vet Surg 33:62-69, 2004.
7. Bernstein AM, Koo HP, Bloom DA: Beyond the Trendelenburg position: Friedrich Trendelenburg’s life and surgical contributions. Surgery 126:78-82, 1999.
8. Richter KP: Laparoscopy in dogs and cats. Vet Clin North Am Small Anim Pract 31:707-727, ix, 2001.
9. Rothuizen J: Laparoscopy in small animal medicine. Vet Q 7:225-228, 1985.
10. Austin B, Lanz OI, Hamilton SM, et al: Laparoscopic ovariohysterectomy in nine dogs. J Am Anim Hosp Assoc 39:391-396, 2003.
11. Dusterdieck KF, Pleasant RS, Lanz OI, et al: Evaluation of the harmonic scalpel for laparoscopic bilateral ovariectomy in standing horses. Vet Surg 32:242-250, 2003.
12. McCarus SD: Physiologic mechanism of the ultrasonically activated scalpel. J Am Assoc Gynecol Laparosc 3:601-608, 1996.
13. Bailey JE, Freeman LJ, Hardie RJ: Endosurgery, in Bojarab WJ (ed): Current Techniques In Small Animal Surgery. St. Louis, Williams and Wilkins Company, 1998, pp 729-741.
14. Van Goethem BE, Rosenveldt KW, Kirpenstein J: Monopolar Versus Bipolar Electrocoagulation In Canine Laparoscopic Ovariectomy: A Nonrandomized, Prospective, Clinical Trial. Vet Surg 32:464-470, 2003.
     

Introduction

Cesarean section in the dog and cat usually is an emergency procedure because prolonged dystocia risks the life of the mother and neonate. Cesarean section can be planned and performed before the onset of active parturition when dystocia is predicted owing to preexisting injuries or abnormalities that compromise the birth canal. Cesarean section is indicated when dystocia results from primary uterine inertia, when secondary uterine inertia has occurred in protracted dystocia of over 24 hours’ duration, when obstructive dystocia (e.g., grossly oversized fetus or abnormally small pelvic canal) is present, or when removal of the obstructive fetus is not likely to alter the ultimate outcome of the dystocia.

Surgical Anatomy

The gravid uterus lies on the abdominal floor during the last half of pregnancy. The heavily gravid uterine horns are parallel and in contact with each other, unlike the divergent uterine horns in the non-pregnant animal. As the horns enlarge, they also flex and bend the uterus cranially and ventrally on itself. When making the abdominal incision during cesarean section, the surgeon must be aware that the uterus is close to the thin, distended abdominal wall.

The uterus is composed of three layers: tunica serosa (perimetrium), tunica muscularis (myometrium), and mucosa (endometrium). The tunica serosa is a layer of peritoneum that covers the entire uterus and is continuous with the mesometrium (broad ligaments). The muscular layer consists of a thin longitudinal outer layer and thick inner layer. The deeper myometrium contains blood vessels, nerves, and circular and oblique muscle fibers. The tunica muscularis is the layer of greatest tensile strength. The tunica mucosa is the thickest of the three layers.

The uterus is well supplied with arterial blood from the ovarian and uterine arteries (See Figure 33-1). The uterine vessels greatly enlarge during gestation and potentially complicate an ovariohysterectomy performed in conjunction with a cesarean section. Lymphatic drainage of the uterus is through the internal iliac and lumbar lymph nodes. Autonomic nervous innervation is through the hypogastric and pelvic plexuses.

Preoperative Preparations

Animals considered for cesarean section are often in poor physiologic condition at the time of presentation and should be carefully examined. Abdominal radiographs are useful in documenting the presence and number of fetuses, thus helping the surgeon to avoid inadvertently leaving a fetus in the uterus or pelvic canal. Laboratory tests are often limited to measurement of the animal’s hematocrit, total plasma protein, serum urea nitrogen, or urine specific gravity. These tests assist in evaluating the need for corrective fluid therapy or cross matching of potential blood donors. Most pregnant animals are mildly anemic because of an increase in plasma volume during gestation without a concomitant increase in red blood cells. The surgeon should consider this physiologic anemia when deciding whether the dam requires a whole-blood transfusion.

An intravenous fluid infusion should be established before any anesthesia is given. The preferred fluid is a balanced electrolyte solution such as lactated Ringer’s solution. A solution of 2.5% dextrose and half-strength lactated Ringer’s may be more appropriate if the animal has not eaten for some time and hypoglycemia is suspected. A baseline administration rate of 10 mL/kg/hr may be increased as indicated by physiologic parameters. All volume deficits should be corrected before the surgical procedure is begun, if possible. If the fetuses are known to be dead and decomposing or if uterine infection is established, intravenous antibiotic therapy (cephalothin sodium, 40 mg/kg IV, or cefazolin sodium 22 mg/kg IV) should be instituted at this time.

The surgeon and the client should discuss, before surgery, the nature of the surgical procedure, its potential complications, and the issue of simultaneous ovariohysterectomy. The length of the surgical procedure may be important, depending on the condition of the dam. The advisability of an additional operation for ovariohysterectomy should be carefully considered. Ovariohysterectomy may be better postponed until the litter is weaned and the uterine vasculature has returned to normal size.

Surgical Technique

The dam is clipped from the xiphoid to the pubis, and the ventral abdomen is initially prepared by surgical scrubbing before induction of anesthesia to reduce total anesthesia time. Anesthesia induction and intubation are performed on the operating table. Usually, the dam has not been fasted before anesthesia; therefore, the patient should be intubated rapidly to minimize the risk of aspiration should vomiting occur during induction of anesthesia.

Operative speed is important in cesarean sections because prolonged “incision-to-delivery” time is associated with increased fetal asphyxia and depression. A 10 to 20° left or right lateral tilt from dorsal recumbency is frequently used in women to prevent supine hypotension syndrome, which is thought to result from compression of the gravid uterus on the posterior vena cava, thus reducing venous return. Supine hypotension syndrome does not occur in the full-term pregnant bitch due to the bicornuate uterus and its position during pregnancy. Maternal posture has no effect on systemic blood pressure, therefore dorsal recumbency is an acceptable position for cesarean sections in dogs and cats.

After induction of anesthesia, the patient’s limbs are tied down, and the final surgical preparation of the ventral abdomen is rapidly completed. The ventral abdomen is four-quadrant toweled and is draped from the xiphoid to the pelvic brim, to allow room for extension of the abdominal incision if necessary.

A ventral midline incision is made commencing at the umbilicus. The length of the incision is determined by the estimated size of the uterus. The mammary glands often are hypertrophied, and the surgeon should not invade mammary tissue when making the skin incision. The surgeon should also remember that the uterus is enlarged and should not be lacerated when the abdominal cavity is entered. I prefer using thumb forceps and a scalpel to open the abdominal cavity; however, Mayo scissors also are acceptable.

After the abdominal incision is completed, the wound edges are protected with laparotomy pads moistened with sterile saline. The first uterine horn and then the second are exteriorized by careful lifting through the incision. The surrounding and underlying viscera are packed off with additional moistened laparotomy pads to prevent abdominal contamination with fetal fluids. A small incision with a scalpel is then made in a relatively avascular area on the dorsal or ventral aspect of the uterine body; one must be careful not to lacerate a fetus inadvertently with the scalpel. The uterine incision is then extended with scissors to a length sufficient for easy removal of the fetuses (Figure 33-10).

In dystocia, the fetus present in the uterine body should be removed first. Each fetus is brought to the incision by gently “milking it down” the uterine horn. This is done by squeezing the uterine horn proximal to the enlargement. Once the fetus is near the incision, it may be grasped, and gentle traction may be applied to facilitate rapid removal from the uterus (Figure 33-11).
 

As each fetus is removed, the amniotic sac is broken to allow breathing to begin (Figure 33-12). Fetal fluids should be removed from the operative field by suction to minimize contamination. The umbilical vessels are then clamped and are severed approximately 2 to 3 cm from the fetal abdominal wall (Figure 33-13). The neonate is placed on a sterile towel and is passed to an attendant. The associated placenta is then slowly removed from the endometrium by gentle traction to minimize hemorrhage. This procedure is repeated until all fetuses and placentas have been removed. If considerable difficulty is encountered in mobilizing the fetuses down the uterine horns, additional incisions can be made in the horns. Before closure, the uterus is palpated from the pelvic canal to each ovary to be certain that all fetuses and placentas have been removed.

Another method of delivery is to remove the neonate and placenta with the umbilical cord and fetal membranes still intact. The amniotic sac is broken, and the cord is clamped when the neonate has been handed to an attendant. More maternal hemorrhage may be noted with this method.

Once all fetuses have been removed, the uterus rapidly begins to contract; this contraction is important in arresting hemorrhage. If the uterus has not begun to contract at the time of closure, oxytocin (5 to 20 units intramuscularly) can be administered.

I prefer absorbable suture material such as polydioxanone or polyglyconate with swaged-on noncutting needles for uterine closure. The edges of the uterine incision are carefully apposed with an inverting, continuous Cushing pattern followed by a continuous Lembert oversew (Figure 33-14). Before the uterus is returned to the abdomen, the closure should be inspected and the uterus should be cleansed with warmed sterile saline solution. If abdominal contamination has occurred during the surgical manipulations, the abdomen should be liberally lavaged with warmed sterile saline solution. The omentum is replaced over the uterus and other abdominal viscera before abdominal closure; the linea alba is closed with simple interrupted sutures of appropriate-sized absorbable suture material. Nonabsorbable suture material, such as polypropylene, nylon, or stainless steel wire, may also be used to close the linea alba. The subcutaneous tissue is closed with 3-0 or 2-0 absorbable suture, and the skin is closed with nonabsorbable suture.
 

Before the conclusion of the surgical procedure, all inhalation anesthetic agents are discontinued, and the dam is weaned from assisted ventilation by progressively decreasing the respiratory rate. The dam should then be given several maximal inspirations to reopen any atelectatic areas of lung before a return to breathing room air.

Extubation should not be too hasty because patients that undergo cesarean section may have full stomachs and may vomit during induction or recovery. Vomiting during recovery is a major problem in parturient women, but it is less important in the dog and cat.

Resuscitation of the Neonates

After the neonate has been handed to the assistant, its umbilical cord should be temporarily clamped, the fetal membranes should be removed (if this has not yet been done), and its viability should be ascertained. If a heartbeat can be palpated, the nasopharynx should be cleared of fluid and mucus by gentle suction or cotton swabs. If a suction apparatus is not available, a bulb syringe can be used for suction. A gentle, controlled, downward swing of the neonate may help to clear fluid from the upper airways by centrifugal force. The neonate is then vigorously dried because skin stimulation stimulates respiratory drive in a reflex manner.

The neonate should be breathing and crying by this stage. Other encouraging signs are pink mucous membranes and a strong pulse. More active resuscitative measures include narcotic antagonists such as naloxone (0.01 mg/kg IM or IV) and the respiratory stimulant doxapram (1 to 2 drops sublingual or 0.1 ml IV in the umbilical vein). In the event of cardiorespiratory collapse, an emergency endotracheal intubation may be attempted with a plastic intravenous catheter (18 to 20 gauge).

Postoperative Care of the Dam and Neonates

When the puppies or kittens have been resuscitated and dried, they should be kept in a warm environment to avoid chilling. The clamp is removed from the umbilical cord, which is checked for hemorrhage. If hemorrhage occurs, the cord should be ligated with 3-0 chromic gut.

While the mother is recovering from anesthesia, her mammary glands should be cleaned with warm water to remove any residual surgical preparation solutions, blood, or fetal fluids. The dam should be returned to her litter as soon as she has recovered. The dam should continue to be carefully watched by the veterinarian or the owner in the first hours after the operation because sudden lapses into shock can occur if uterine bleeding recommences.

Colostrum is important to the neonates. Although some transplacental acquisition of passive immunity occurs before birth, most antibodies are transferred through the colostrum after birth. Nursing also stimulates the release of oxytocin to mediate uterine contraction. Although drugs can be transferred to the neonate in the milk, this is not important unless drugs are administered to the mother on a continuing basis. Drugs that are weak bases and become ionized at a low pH usually accumulate in the milk at a higher concentration than in the dam’s blood.

Before the litter is discharged, puppies or kittens should be inspected for obvious congenital abnormalities, such as deformed limbs, cleft palate, and imperforate anus. This check, together with advice to the owners on neonatal care, ensures good veterinarian-client relations. The dam and her litter can be discharged as soon as she is able to stand and appropriate behavior patterns toward the litter are confirmed. Owners should be instructed to monitor the dam carefully for the next 24 to 48 hours. They should look for evidence of continued uterine hemorrhage, anorexia, or signs of infection or dehiscence of the abdominal incision. The dam should be returned in 7 to 10 days for suture removal.

Postoperative Complications

Certain complications are associated with both emergency and elective cesarean section. Perioperative maternal mortality rates of over 4% have been reported, perhaps owing to the emergency nature of the operation and the patient’s stressed condition at the time of surgery. Hypovolemia and hypotension are the most common complications and are treated with vigorous fluid therapy or blood replacement. Hemorrhage of uterine origin should be controlled with oxytocin (5 to 20 units IM or IV). In severe hemorrhage, the dosage may be repeated after 2 to 4 hours, and whole blood transfusion may be started. Persistent hemorrhage may require an emergency ovariohysterectomy. If an infected uterus is encountered during the surgical procedure, ovariohysterectomy or packing of the uterus with antibiotic boluses and systemic antibiotics should be considered.

Postoperative peritonitis should not be a problem unless a break in surgical technique or abdominal contamination with septic uterine contents has occurred. Infection can be controlled with careful surgical technique, intraoperative abdominal lavage, and antibiotic therapy in most cases. Agalactia may occur in the queen or bitch after cesarean section, but normal milk flow usually occurs within 24 hours. Oxytocin (0.5 units/kg intra-muscularly) may be administered to stimulate milk production if necessary. Excessive depression of either the mother or the offspring after anesthesia indicates that one should critically review the anesthetic protocol for reduction in doses of analgesics or barbiturate depressants.

Suggested Readings

Abitbol MM: Inferior vena cava compression in the pregnant dog. Am J Obstet Gynecol 130:194, 1978.

Gilroy BA, DeYoung DJ: Cesarean section. Vet Clin North Am 16:483, 1986.

Macintire DK: Emergencies of the female reproductive tract. Vet Clin North Am 24:1173, 1994.

Moon PE, Erb HN, Ludders JW, et al: Perioperative management and mortality rates of dogs undergoing cesarean section in the United States and Canada. J Am Vet Med Assoc 213:365, 1998.

Probst CW, Webb AI: Postural influence on systemic blood pressure gas exchange, and acid/base status in the term-pregnant bitch during general anesthesia. Am J Vet Res 44:1963, 1983.

Probst CW, Broadstone RV, Evans AT: Postural influence on systemic blood pressure in large full-term pregnant bitches during general anesthesia. Vet Surg 16:471, 1987.
 

Indications

Traditional cesarean section (hysterotomy) has been the treatment of choice for canine and feline dystocia that is not responsive to medical management. Hysterotomy is a well described and widely accepted technique. Most references advise against ovariohysterectomy at the time of hysterotomy, citing additional stress to the female, increased blood loss, longer anesthetic time, and problems with neonatal survival.^1,3 Sometimes, no reason is specified.⁴ Many practicing veterinarians have performed ovariohysterectomy for dystocia in the dog and cat with excellent results. The technique of “en bloc” cesarean section (ovariohysterectomy) followed by rapid removal of neonates from the gravid uterus) has been shown to be safe and effective for both cats and dogs.⁵ Future reproduction is impossible after this technique, a fact that pleases most owners. The technique described is easier, quicker, and has less chance for intra-operative contamination than traditional cesarean section.

Surgical Technique

Preoperative considerations and anesthetic techniques are identical to those for routine cesarean section. A caudal ventral midline incision is made through the skin, subcutaneous tissue, and linea alba of the abdomen. Care is taken as the linea is incised to not lacerate the large gravid uterus which may be in contact with the ventral abdomainl wall. The incision is packed off with sterile, saline moistened laparotomy sponges. The gravid uterus is exteriorized, and the uterine horns are laid out laterally to the incision (Figure 33-15). Next, the suspensory ligaments are cut or broken to allow mobilization of the ovaries by their vascular pedicles. No clamps are applied at this time. The broad ligament is broken down manually or incised on both sides of the uterus from the ovarian pedicle to the cervix. This leaves the blood supply to the uterus and fetuses intact while freeing up all attachments except the ovarian pedicles and the uterine body (Figure 33-16).

Ovariohysterectomy can now be performed rapidly and safely, with a maximum of no more than 45 to 60 seconds elapsed between clamping of the ovarian pedicles and uterine body and delivery of the neonates by assistants. The surgeon palpates the patient’s cervix and vagina to check for a fetus. If one is present, it is manipulated gently back into the uterine body. Two hemostatic clamps are placed across each ovarian pedicle, and three clamps are placed across the uterine body just distal to the cervix. A moistened laparotomy pad is placed to minimize any abdominal contamination from the uterine incision. The gravid uterus and ovaries are removed by dividing between the clamps (Figure 33-17). The surgeon hands the gravid uterus to a team of assistants, who immediately open the uterus and resuscitate the neonates. The ovarian pedicles and uterine stump are ligated with chromic gut or other absorbable suture sized according to the surgeon’s preference. The abdomen is closed routinely. Subcuticular sutures are preferred over skin sutures to prevent irritation of the suture line by the nursing pups. Appropriate postoperative pain relievers, such as oxymorphonc (0.03 to 0.1 mg/kg) intravenously, intramuscularly, or subcutaneously, morphine sulfate (.1 to .5 mg/kg) subcutaneously or intramuscularly, or buprenorphine (5 to 10 ug/kg intravenously, intramuscularly, or subcutaneously), are given after the uterus has been removed.
 

Resuscitation of the Neonates

The gravid uterus is handed to an assistant after removal, who takes it from the sterile operating room to a location previously prepared for neonatal resuscitation. The uterus is opened with scissors or a scalpel blade (Figure 33-18), taking care not to cut a fetus. The neonates are rapidly removed and resuscitated by the assistants. Ideally, one assistant should be available to treat each neonate, although one person can care for two or three neonates at a time if they are healthy. Hypoxia is thought to be one of the primary reason for neonatal mortality.⁶ The mortality rate of puppies and kittens delivered by ovariohysterectomy is reportedly lower than the mortality rates by either traditional cesarean section or natural parturition.⁵ This finding suggests that ovariohysterectomy for the treatment of dystocia has no adverse effect on neonatal survival.
 

Contraindications for Ovariohysterectomy

No important complications or contraindications for this technique have been described.⁵ Some limitations include the need for multiple assistants for simultaneous neonatal resuscitation of a large litter and the loss of future reproductive capability (although this is usually considered an asset). Anemia is not a complication with this technique, because no significant decrease in packed cell volume was reported in either dogs or cats undergoing cesarean section by ovariohysterectomy.⁵ In a small, significantly anemic female with a markedly engorged uterus, however, hysterotomy followed by rapid involution of the uterus will allow return of some of the uterine blood to the peripheral circulation before removal of the nongravid uterus.

Advantages of Ovariohysterectomy

Ovariohysterectomy for dystocia is rapid and safe for both the bitch and the neonate. Use of this technique minimizes anesthetic time and reduces intraoperative peritoneal contamination by uterine contents, which may occur during hysterotomy. Both dogs and cats continue to lactate normally as long as the babies continue to nurse. There is scant to no postoperative lochial discharge, as is common for several days after birth because the uterus has been removed. Ovariohysterectomy also provides an opportunity for future population control in pets that are unable to reproduce naturally or whose owners may not be able to afford a second operation for sterilization of the animal in the future. The health of the mother and of the neonates is not compromised when cesarean section by ovariohysterectomy is used as the surgical treatment for dystocia.

References

1. Herron MR. Herron MA. Surgery of the uterus. Vet Clin North Am 1975;5:471 476.
2. Probst CW, Webb M. Cesarean section in the dog and cat: anes¬thetic and surgical techniques. In: Bojrab AU, ed. Current tech¬niques in small animal surgery. 2nd ed. Philadelphia: Lea & Fee¬iger, 1983:346 351.
3. Gaudet DA, Kitchell BE. Canine dystocia. Compend Contin Educ Pract Vet 1985;7:406 418.
4. Probst CW. Uterus: cesarean section. In: Bojrab AU, ed. Current techniques in small animal surgery. 3rd ed. Philadelphia: Lea & Febiger, 1990:404 408.
5. Robbins MA, Mullen, HS. En bloc ovariohysterectomy as a treatment of dystocia in dogs and cats. Vet Surg 1994; 23: 48 52.
6. Fox MW. Neonatal mortality in the dog. J Am Vet Med Assoc 1963;143:1219 1223.