Feline urinary diversion procedures (Proceedings)

Urine diversion techniques are performed to temporarily or permanently divert urine from its normal anatomic course from the kidney through the ureter to the bladder and finally through the urethra. Veterinarians are most familiar with temporary urine diversion (urethral catheters) that are often used to stabilize animals that are sick as a result of metabolic changes associated with urinary tract obstruction. Temporary diversion (peritoneal drainage) may also be used as a bridge to more definitive surgical procedures such as repair of a ruptured urinary bladder.

Permanent urinary diversion is performed as a surgical procedure to redirect or reconstruct portions of the urinary tract that have been damaged by trauma or neoplastic involvement or for palliation of recurring urethral obstruction. Most permanent procedures performed in animals have been to circumvent areas of the urethra prone to obstruction with calculi or mucus plugs.

Temporary Diversion

      A. Urethral

      1. Useful for maintaining patency of urethra in obstructed animals, measurement of urine production in animals with renal disease, and as stents to allow uroepithelium to migrate over tears or lacerations to the urethra.

      2. Soft rubber or silicone preferable to polypropylene and should be connected to a "closed" urinary system.

      3. We do NOT routinely administer antibiotics to animals with indwelling catheters (selection for hospital/resistant pathogens) BUT we do urine culture and sensitivity when we remove the catheters.

      B. Prepubic urinary diversion

Tube Cystostomy is an easily performed urinary diversion procedure that allows drainage of urine from animals where indwelling urethral catheters cannot be passed. Has also proven useful as a palliative procedure for those animals with neoplastic disease of the bladder/urethra.

      1. Identical procedure to "feeding tube gastrostomy" tube placement but using the bladder.

      2. Place a purse-string suture in the rostral 13/rd of the ventral bladder wall using absorbable suture.

      3. Make a stab incision in the middle of the purse-string and insert a Foley or Pezzar catheter into the bladder (AFTER passing it through the abdominal wall first) and tighten the purse-string.

      4. Place a "pexy" suture both cranially and caudally between the bladder wall and the abdominal wall using absorbable suture.

      5. Connect the catheter to a closed urinary collection system.

Perineal Urethrostomy (PU)

Attempts at PU in the feline were made initially in the 1950's by Carbone. Initial attempts failed because of the lack of recognition that the obstruction occurred in the penile urethra and initial urethrostomy techniques excised only the distal portion of the penile urethra. Over the next 15-20 years, surgery evolved/improved and the classic Wilson-Harrison urethrostomy was described in 1974. Other variations of the technique have been described but the basic principals remain unchanged. MANY PU's were performed in the 1970's and 1980's and continue to be performed today although total numbers have decreased due to dietary management used with Feline Urologic Syndrome (FUS). A report from the U. of Minnesota described the frequency of this disease (FUS) as declining from 40 cases/1000 cats evaluated in the 1980's to 20 cases/1000 cats evaluated in the 1990's. Similarly, the frequency of urethrostomy decreased from 19/1000 cats in the 1980's to 2 casaes/1000 cats in the 1990's. There is some evidence that the prevalence of calcium oxalate stones in cats have increased over the past 10 years probably due to popular acidifying diets.

A. Indications/Rule outs for PU

     • -Repeated obstruction due to FUS/FLUTD

     • -Surgery is economically feasible when one considers the economics of repeated obstruction

     • -Regardless of underlying cause (many have been postulated), obstruction tends to occur in the penile urethra. Various exacerbating causes have been described including stress, low water consumption, diet, obesity, etc. Bacterial infection is RARELY a contributing factor to the disease unless the animal has been previously catheterized thus antibiotic usage does NOT influence the disease process.

     • -Radiographs contrast procedures are indicated to rule out cystic/urethral calculi prior to performing urethrostomy

B. Procedure

      1. The animal is placed in sternal recumbency (perineal position) OR in dorsal recumbemcy with the rear limbs pulled cranially.

      2. Place a purse-string suture in the anus if sternal recumbency is elected.

      3. An elliptical incision is made to encompass the scrotum and penis. (If the animal is intact I neuter him first in a normal fashion.

      4. Subcutaneous tissue is dissected and the ischiocavernosus muscles exposed bilaterally.

      5. I incise the muscles bilaterally as close to their origin on the ischium as possible; other surgeons prefer to incise their insertion on the penis.

      6. The ventral penile ligament and pelvic fascia are incised ventrally allowing blunt digital dissection ventrally to free up the pelvic urethra to the pelvic (pubic brim).

      7. It is critical to free up the urethra to the level of the bulbourethral glands (BUG). These glands are located just rostral to the ischiocavernosus muscles and mark the beginning of the pelvic urethra.

      8. Free up the urethra ventrally, laterally, and SOME dorsally but do NOT be overly aggressive dorsally as this may result in damage to the external anal sphincter, caudal rectal nerve, and anal sacs. Stay as close to the urethra as possible dorsally.

      9. The retractor penis muscle is freed from the dorsum of the penis and the distal urethra excised.a through-and-through mattress suture is placed through the remainder of the urethra to decrease hemorrhage from incised cavernous tissue.

      10. The urethra is incised longitudinally with sharp-sharp iris scissors to the level of the BUG'S.

      11. Place 2-3 corner sutures to begin the suturing of urethral mucosa to skin. Picking up small bites of mucosa and including a small bite of surrounding tissue will compress bleeding cavernous tissue. I use 4-0 polypropylene suture on a tapered needle; any 3-0 or 4-0 minimally reactive suture is acceptable (nylon).

      12. After the first several sutures, a continuous pattern may be placed to appose skin and urethral mucosa.

      13. No urethral catheters are used or placed in the postoperative period.

      14. REMOVE THE PURSE-STRING!!

      15. Remove sutures under sedation in 10-14 days.

Most common serious complication is stricture ; usually caused by NOT getting to the pelvic urethra proximally, sloppy suturing of the pelvic urethra to skin could also contribute. More severe complications including fecal and urinary incontinence have been reported but are rare and due to overly aggressive surgical technique especially in the area dorsal to the urethra.

These animals should be monitored periodically (every 6-12 months) for bacteruria as asymptomatic UTI has been shown to be more common in cats post PU.

Antepubic Urethrostomy

A. Indications

      1. Persistent stricture secondary to poorly constructed PU's.

      2. Pathology within the more rostral pelvic urethra, and skin loss in the perineal area preventing PU.

B. Procedure

      1. The animal is placed in dorsal recumbency and a caudal ventral midline incision made from the umbilicus to the pubis.

      2. The abdomen is entered and a "stay suture" placed in the cranial aspect of the bladder.

      3. The urethra is isolated by gently separating periurethral fat caudal to the urinary ladder.

      4. SAVE as much urethra as possible; this is enhanced by using rongeurs to perform pubic ostectomy to expose more intrapelvic urethra; ligate and incise the urethra caudally.

      5. Free the urethra proximally and CONSERVATIVELY; DO NOT excessively dissect in the fat on the dorsal urethra at the bladder neck or incontinence is likely.

      6. Split (spatulate) the urethra on its ventral border for 1.0-1.5 cm and bring this portion to the skin. The stoma MAY be part of the primary incision or be placed outside the incision (laterally).The abdominal wall is carefully closed taking care to not decrease the diameter of the urethra.

      7. The urethral spatulation is sutured to the skin with 4-0 polypropylene.

      8. Remove sutures at 10-14 days postoperatively.

Over all actually an easier surgical procedure than PU but the risk of incontinence prohibits its use routinely. Animals should be monitored long-term for bacteruria. A recent retrospective study of 16 cases revealed incontinence and/or skin ulceration in 6 of the 16 cases. This was serious enough to result in euthanasia.

Remember 2 factors when performing this procedure:

     • -MAINTAIN AS MUCH URETHRAL LENGTH AS POSSIBLE

     • -MINIMIZE DISSECTION at the bladder neck.

References

1. Lekcharoensuk C, Osborne CA, Lulich JP. Evaluation of trends in frequency of urethrostomy for treatment of urethral obstruction in cats. J Am Vet Med Assoc 2002;221:502-505.

2. Baines SJ, Rennie, S, White RAS. Prepubic Urethrostomy: A long-term study in 16 cats. Vet Surg 2001;30:107-113