Author

Stephen J. Birchard DVM, MS, Diplomate ACVS

Wednesday, October 1, 2014

Scrotal Urethrostomy in Dogs: Good surgical technique makes all the difference.

Urethrostomy is the surgical procedure that creates a permanent opening between the urethral lumen and the skin, and is indicated for several disease conditions such as recurrent urinary obstruction due to calculi, trauma or neoplasia.  Urethrostomy in the dog can also be performed when penile amputation is necessary for neoplasia or other conditions, such as hypospadias.

Several types of urethrostomy have been described for dogs, but scrotal urethrostomy is currently the procedure of choice.(1-3) After castration and scrotal ablation, the urethra is opened at the level of the scrotum and sutured to the adjacent skin.

Advantages of scrotal urethrostomy are:
  • the urethrostomy stoma is located ventrally on the dog, minimizing urine scald of surrounding skin
  • the urethra is relatively close to the skin at this location
  • the scrotal portion of urethra is large enough to allow formation of a large stoma that allows passage of calculi and rarely strictures
  • urinary continence is not compromised by developing a stoma at this location.

           
Surgical Technique for Scrotal Urethrostomy

Under general anesthesia place the dog in ventral recumbency. If possible, pass a urinary catheter to flush calculi retrograde into the urinary bladder (if applicable), and leave in to help with identification of the urethra during dissection. Prepare the scrotum, ventral abdomen, and ventral perineum for aseptic surgery. Make an elliptical incision around the base of the scrotum. Be sure to leave sufficient skin to allow for a tension-free closure of skin to urethral mucosa. Perform scrotal ablation and castration in a routine fashion. (Fig. 1)  
Fig. 1: Beginning of a scrotal ablation by performing castration and scrotal ablation.
Dissect through the subcutaneous tissue and identify the retractor penis muscle. (Fig. 2) Dissect the muscle away from the urethra and retract it laterally to the urethra using forceps or a stay suture. 
Fig. 2: Dissection through the subcutaneous tissue exposing
the retractor penis muscle (black arrow), and urethra(white arrow).
Incise the urethra on the midline with a scalpel (4-6 cm opening). (Fig. 3a,b) 
Fig. 3a: Incision is made on the urethral midline with a scalpel.
The incision can be started with a scalpel and extended with fine scissors.
Fig. 3b: Completed urethral incision. Note urinary catheter in the urethral lumen.

Suture the urethral mucosa and submucosa to the skin with fine suture material (4-0 PDS or Monocryl, swaged-on taper needle) in a simple continuous pattern. (Figs. 4-9) Start the suture line at the caudal aspect of the incision, and work cranially. 
Fig. 4: Surgical model of the penis and tissue layers important for urethrostomy.
(TA = tunica albuginea)
Fig. 5: Closure of the urethrostomy begins with 2 lines of sutures at the caudal aspect of the incision.
 Place the sutures in a “3-bite” manner: urethral mucosa first, then the tunica albuginea (fibrous covering of the corpus cavernous urethra), then a split-thickness bite of the skin. This helps to close and seal the cavernous layer of tissue, preventing excessive postoperative hemorrhage. The simple continuous pattern performed in this manner drastically reduces postoperative bleeding. (2)
Fig. 6: The first line of simple continuous suture is being placed.
Note the inside out direction of the suture bites (arrow). Include small bites of
the mucosa, tunica albuginea, and skin. ("3-bite" technique)
Fig. 7: Completion of one side of the closure.

Fig. 8: Completion of both sides of the urethrostomy
Avoid excessive manipulation of the urethral mucosa since it is friable and will bleed more with trauma.
Fig. 9: Appearance of a healed scrotal urethrostomy 2 weeks postoperatively.
Postoperative Care

Typical postoperative care after scrotal urethrostomy involves prevention of incisional trauma by using an Elizabethan collar on the dog, applying petroleum jelly around the incision to keep it moist and clean, close monitoring of the incision for swelling or bruising, and general supportive care (e.g., analgesics). Light sedation with acepromazine (0.05 mg/kg, SQ or IM) can be helpful to reduce hemorrhage from the incision site which is the most common postoperative complication. Suture removal is not necessary when absorbable suture is used to close the urethrostomy. If persistent hemorrhage occurs (i.e., for several days after surgery), carefully re-assess the incision for areas where the mucosa has not properly healed to the skin.  Additional sutures in these areas to close the defect should alleviate the problem.

Postoperative urethral stricture, although a possible complication of urethral surgery, is uncommon in a well-performed scrotal urethrostomy. Stricture may occur due to chronic licking of the incision or poor apposition of the urethral mucosa to skin during closure. Treatment of stricture is to revise the urethrostomy and insure meticulous mucosa to skin closure.

References

1. Bilbrey SA, Birchard SJ, Smeak DD. Scrotal urethrostomy: A retrospective review of 38 dogs (1973 through 1988). J Am An Hosp Assoc 1991; 27: 560-564.

2. Newton JD, Smeak DD. Simple continuous closure of canine scrotal urethrostomy: Results in 20 cases. J Am An Hosp Assoc 1996; 32:531-534.

3. Collins RL, Birchard SJ, Chew DJ, Heuter KJ. Surgical treatment of urate calculi in Dalmatians: 38 cases (1980-1995). J Am Vet Med Assoc 1998; 213:833-838.