Penis and Prepuce

Amputation Techniques

Partial or “complete” amputation of the penis may be indicated in certain congenital, traumatic, or neoplastic conditions. The most common neoplasm of this area, transmissible venereal tumor, is generally responsive to chemotherapy or radiotherapy. Thus, amputation of the penis should be considered rarely, if ever, as a corrective measure for this condition. Cryotherapy has also been used successfully for removal of benign tumors of the penis.

Partial Amputation

The exact location of the amputation is determined by the site of the lesion. In most cases, the penis can be extruded (Figure 36-1A) and held in the extruded position by clamping the preputial orifice with a towel clamp just caudal to the bulbus glandis. The sheath can be opened full thickness on the ventral midline, when necessary, to expose the penis. The penis can be extruded through a ventral opening in the prepuce, or the entire length of the prepuce can be opened for better exposure. A Penrose drain tube works well as a tourniquet around the base of the penis.

Amputation of the tip of the penis may be necessary in patients with chronic or recurrent prolapse of the urethra (Figure 36-1). Placing a catheter in the urethra helps to identify the limits of the lumen. The surgeon should make the incision partway across the tip, place a stay suture to unite the mucosa of the urethra with the mucosa of the penis, and then complete the excision of the tip of the penis (Figure 36-1B). The triangula-tion technique (Figure 36-1C and D) conserves a patent lumen to the tip of the urethra. Careful apposition of the cut mucosal edges to the penile tunica helps to avoid excessive scar tissue proliferation and stricture. A continuous suture pattern helps to control seepage from the cavernous erectile tissue. Synthetic absorbable suture is used for mucosal closure.
 

An Elizabethan collar or a side-bar restraint device should always be used to prevent the patient from licking the wound. Castration or careful hormone therapy may be indicated to help to prevent erection during healing.

Amputations of the main body of the penis require the severing of the os penis, as well as the salvaging of enough urethra distal to the severed os penis for a distance of 1 cm. The os penis and urethra are severed with bone-cutting forceps and a scalpel. The urethra is isolated subperiosteally from the groove of the os penis with a small dental chisel. The urethra is split, flared, trimmed, and sutured to the infolded tunica albuginea, as shown in Figure 36-2. Care should be taken to appose the mucosal surfaces. Although it is perhaps easier to achieve excellent apposition with fine, closely placed interrupted sutures, a continuous pattern is more likely to control bleeding. Some bleeding, especially at the end of urination, is common, even for several days after the operation. It is difficult to identify and to ligate individual vessels in this area. Releasing the tourniquet while the wound is open, in an effort to identify and to ligate the vessels within the corpus spongiosum penis, may prove unrewarding.
 

Preputial Amputation

When pooling of urine within the prepuce becomes a concern after partial amputation of the penis, shortening of the entire prepuce may be desirable. For the best cosmetic results, a full-thickness section of the prepuce can be removed (Figure 36-3). The length of prepuce to be removed should be the same as the length of the penile resection. In patients with congenital micro-penis, the tip of the prepuce should cover the tip of the penis by approximately 1 cm. The cranial transverse incision is made 2 cm caudal to the cranial junction of the prepuce and the body wall, to allow adequate circulation to the cranial end of the prepuce. The location of the caudal transverse incision is determined by the length of the penis. The two incisions are extended laterally in an elliptic fashion to facilitate a smooth closure of the skin.

Next, the dorsal aspect of the section of prepuce to be removed is dissected free from the body wall with scissors. With careful dissection, most of the preputial vessels, which lie immediately subcutaneously on both sides of the sheath, can be identified and preserved. To close the amputation, the preputial mucosa is apposed with 4-0 absorbable suture, using a submucosal pattern. If a continuous pattern is used around the circumference of the prepuce, care should be taken to avoid a pursestring effect, which limits the movement of the penis. The veterinarian may find it easier to close the dorsal mucosa if the penis is allowed to protrude through the incision site during this phase of closure.

Complete Amputation

The initial skin incision is made in an elliptic fashion around the entire external genitalia (Figure 36-4A). The preputial vessels are ligated, as are any additional branches of the caudal superficial epigastric vessels that cross the incision line. The spermatic cords are isolated, ligated, and severed. Care must be taken to place the ligatures tightly enough to prevent retraction of the severed spermatic artery if the tunicae are incorporated in the ligature. When the penis and the prepuce have been stripped from the body wall in a caudal direction, the dorsal penile vessels are identified and ligated just caudal to the level of the desired penile amputation site. The retractor penis muscle is reflected from the urethra, and, with a catheter in place, a midline incision is made into the urethral lumen at the desire urethrostomy site. A 1-0 absorbable, ligature, which circumscribes the penis, is placed just caudal to the amputation site and just cranial to the urethrostomy site (Figure 36-4B), to control seepage bleeding from the erectile tissue further, if necessary. The shaft of the penis is amputated in a wedge fashion, and the tunica albuginea is apposed over the amputation stump. The urethrostomy should be located in the scrotal area whenever possible. Careful apposition of penile urethra and skin edge, as the urethrostomy is completed, minimizes postoperative bleeding and scar tissue formation (Figure 36-4C). Although suture patterns and materials are a matter of choice, a continuous pattern aids in controlling hemorrhage from any incised erectile tissue. The use of synthetic absorbable suture eliminates the need for suture removal.

Particular care should be taken to obliterate dead space, especially cranial to the stump of the amputated penis, when closing the subcutaneous tissue. The use of a restraint device to prevent licking of the surgery site by the patient is imperative.
 

Correction of Hypospadias

Hypospadias is a congenital anomaly of the external genitalia in which the penile urethra terminates caudal to its normal opening. The urethra can terminate at any level from the perineum to the tip of the penis (Figure 36-5) because the urethral folds fail to fuse (See Figure 36-9). In severe cases, the two halves of the scrotum can fail to fuse, the penis fails to develop normally, and the urethra fails to close in the perineal area (Figure 36-6). Frequently, the analog of the urethra can be present as a fibrous cord that runs from the glans penis to the urethral opening and pulls the penis into a deforming ventral curvature (chordae) (See Figure 36-6).

Minimal defects usually require no urethral surgery. The constant extrusion of the tip of the glans penis can often be relieved by closing the prepuce to its normal extent (Figures 36-7 and 36-8) on its caudoventral aspect. Should the resulting orifice be too small to allow extrusion of the penis, the opening can be increased to the desired diameter by enlarging the lumen of the craniodorsal aspect. Simply leaving the orifice larger by not closing the caudoventral defect to its fullest extent can cause the tip of the penis to continue to droop from the prepuce and may thus subject it to continual drying, licking, and trauma.

Caudoventral closure is accomplished by incising the mucocutaneous junction, separating the mucosa from the skin, and closing the two layers individually (Figure 36-8A). Sutures of 4-0 to 6-0 absorbable synthetic material are preferred. Should the orifice need to be enlarged dorsally, one scissor jaw is inserted into the lumen of the prepuce, and the orifice is cut to the needed extent. With a minimum of undermining, the cut mucosal and skin edge can be apposed (Figure 36-8B). Failure to appose the skin and mucosal edges adequately may result in closure by granulation, or, should the patient be allowed to lick out the sutures, stricture formation is likely to follow.

Small urethral defects can be closed successfully with a two-layer closure (Figure 36-9). A catheter is inserted past the defect, and an incision is made at the open mucocutaneous junction around the perimeter. The mucosa is undermined and is closed, as is the skin. Care must be taken not to create a stricture. Skin can be invaginated to close the urethral defect, provided the hair follicles have been destroyed previously.

Rectangular full-thickness bladder wall sections, rolled into a tube, have been used to replace surgically sacrificed sections of urethra (i.e., urethral neoplasms). Oral mucosa has been used as well. After suturing of the grafts into the urethral defect (over a catheter), the skin is undermined as in Figure 36-9C and is closed over the urethral graft. The catheter is left in place for 7 to 10 days. If open-ended catheters are used as stents, the catheter need not be introduced all the way to the bladder. Catheters remain in place much better if they are cut flush with the urethral orifice and are sutured in place by passing one or two sutures through the catheter and the tip of the penis. For major urethral defects, excision of the external genitalia and urine diversion by urethrostomy are the treatments of choice (See Figure 36-4). An elliptic incision is made around the rudimentary penis, prepuce, and scrotum. Dissection from the body wall is carried out in a cranial-to-caudal direction; the surgeon should ligate preputial vessels as they are identified and isolated. Should penile tissue be present near the caudal end of the incision, it can be ligated in its entirety and excised. Ligation of the dorsal artery of penis is accomplished when necessary. The subcutaneous tissue and skin are closed in a routine fashion.
 

Correction of Phimosis

The inability to extrude the penis from the sheath (phimosis) is usually the result of too small a preputial orifice. Because surgical enlargement of the orifice with a ventrocaudal preputial incision can cause persistent extrusion of the glans, the orifice should be enlarged on the craniodorsal surface. A full-thickness incision is made to the desired length with heavy scissors. The severed preputial mucosa is then undermined sufficiently to allow apposition to the ipsilateral skin edge (See Figure 36-8B). The use of a restraint device to prevent licking or chewing is imperative.

Correction of Paraphimosis

The inability to return the penis to the sheath can result in severe trauma or circulatory compromise. The animal can develop necrosis or injury sufficient to require penile amputation. Persistent exposure of the glans can also result in chapping and excessive licking.

Many patients with acute paraphimosis can be managed by noninvasive methods to return the penis to the lumen of the sheath. The extruded and visually edematous penis should be cleansed, and the sheath should be thoroughly irrigated with nonirritating soaps. A combination of massage and locally applied hypertonic and hygroscopic agents, such as sugar, can help to reduce swelling. Once swelling is reduced, the constricting preputial orifice can usually be pulled over the lubricated penile shaft. Preputial enlargement can be accomplished by incision and primary repair of the mucosal and skin layers, to reduce refractory paraphimosis.

On occasion, the tip of the penis can remain exposed when no obvious orifice defects are present. Once the mucosa has been exposed for some time and has become dry and cornified, the skin of the prepuce rolls inwardly as attempts are made to return the penis to its sheath. After adequate cleansing and lubrication, the penis can be returned to its sheath. If the tip of the penis is well covered by the prepuce (at least 1 cm), narrowing of the preputial orifice will probably prevent recurrence (See Figure 36-8A). Should the prepuce not cover the tip of the penis well, cranial movement of the prepuce should be performed (Figure 36-10). This translocation can be accomplished by removing a crescent-shaped piece of skin from the ventral body wall just cranial to its juncture with the prepuce. Care should be taken to preserve the preputial vessels. The preputial muscles, which lie superficial to the rectus abdominis muscles, can then be shortened by either an overlapping technique (Figure 36-10A) or simple excision followed by reapposition (Figure 36-10B). The closure of the subcutaneous tissue and skin is routine.
 

Preputial Reconstruction

A hypoplastic prepuce can be lengthened in a two-step surgical procedure. The first step involves transplanting oral mucosa to a prepared graft site on the ventral body wall immediately cranial to the hypoplastic prepuce; in the second step, the lateral sides of the grafted mucosa are freed, are formed into a tube, and are anastomosed to the isolated mucosa of the cranial end of the prepuce. Single pedicle skin flaps are advanced to the ventral midline from both sides of the ventral body wall to cover the mucosal tube and to complete the cranial extension of the prepuce.

Correction of Ventral Deviation of the Penis

Wedge osteotomies reportedly have been successfully performed to correct ventral penile deviation. The os penis is approached on the dorsal midline over its greatest curvature. The os penis is fractured with a bone cutter, and a small pie-shaped wedge of bone is excised to allow for straightening of the os penis. After wound closure, an open-ended catheter is sutured in place within the urethra and is left for a minimum of 3 weeks. One disadvantage of this procedure is possible damage to the penile urethra at the time of surgery or during healing. Rigid fixation of the os penis should definitely be maintained to help alleviate the likelihood of nonunion or malunion. Animals with congenital anomalies should not be used for reproductive purposes.

Removal of Penile Urethral Calculi

Most urethral calculi causing impairment of urine flow are lodged just proximal to the os penis. On rare occasion, particularly when the groove within the os penis is narrowed, calculi lodge within the penile urethra. This narrowing can be the result of a congenital deformity or injury, with or without fracture of the os penis. Whenever possible, these calculi should be hydropulsed into the bladder. Extraordinary efforts should not be used to relocate these stones, however, because debridement of the urethral mucosa is likely to result in stricture formation.

The penile urethra is approached from a ventral midline incision, after exposure of the penis as in Figure 36-1A or by splitting the prepuce. A catheter is advanced from the urethral orifice caudally to determine the exact location of the obstruction. Ideally, the incision is made exactly on the ventral midline of the penis, to avoid the erectile tissue. The incision is extended caudally 1 to 2 cm, exposing the calculi. On rare occasion, the surgeon may need to rongeur away a part of the wall of the groove in the os penis after carefully elevating the soft tissue, including the urethra, from the bone.

The calculi are grasped with forceps and carefully are removed. The area is flushed with sterile saline, and the catheter is advanced to the bladder, while one checks for the presence of more calculi. A cystotomy is performed if indicated. The penile urethral incision is closed with fine absorbable suture over a catheter with a continuous suture pattern. The penile incision is then closed over the urethra in similar fashion.

Correction of Penile Urethral Strictures

Minimal stricturing of the penile urethra can often be managed by dilating the stricture and leaving an indwelling open-ended catheter in place for 7 to 10 days. More extensive strictures may be better managed with a prescrotal or scrotal urethrostomy, as discussed previously and in Chapter 31, because the urethra is immobile within the groove of the os penis and does not lend itself well to reconstruction.

Correction of Persistent Penile Frenulum

On rare occasions, the penile mucosa may fail to separate from the prepucial mucosa as the puppy matures, and it may serve as an irritant to the pup or may even impair breeding in the mature male. Rarely is this persistent attachment more than a narrow band of tissue that is easily severed.

Suggested Readings

Ader PL, Hobson HP. Hypospadias: a review of the veterinary literature and a report of three cases in the dog. J Am Anim Hosp Assoc 1978; 14:721.

Bennett D, Baugham J, Murphy F. Wedge osteotomy of the os penis to correct penile deviation. J Small Anim Pract 1986;27:379.

Burger RA, Muller SC, et al. The buccal mucosal graft for urethral reconstruction: a preliminary report. J Urol 1992;147:662.

Chaffee VM, Knecht CD. Canine paraphimosis: sequel to inefficient preputial muscles. Vet Med Small Anim Clin 1975;70:1418.

Hayes AG, Pavletic MM, et al. A preputial splitting technique for surgery of the canine penis. J Am Anim Hosp Assoc 1994; 30:291.

Leighton RL. A simple surgical correction for chronic penile protrusion (dog). J Am Anim Hosp Assoc 1976; 12:667.

Pope ER, Swaim SF. Surgical reconstruction of hypoplastic prepuce. J Am Anim Hosp Assoc 1986,22:73.

Poppas DP, Mininberg LH, et al. Patch graft urethroplasty using dye enhanced laser tissue welding with a human protein solder: a preclinical canine model. J Urol 1993; 150:648.

Proescholdt TA, DeYoung DW, Evans LE. Preputial reconstruction for phimosis and infantile penis. J Am Anim Hosp Assoc 1977; 13:725.

Smith MM, Gourley IM. Preputial reconstruction in a dog. J Am Vet Med Assoc 1990,196:1493.

Varshney AC, Sharma VK, et al. Surgical management of carcinomatous urethral obstruction in a dog. Indian Vet J 1985; 62:1073.