URETHRAL OBSTRUCTION IN MALE CATS
Overview of the condition
Male cats can easily develop obstruction of the urethra- the tube draining urine from the bladder out of the penis- because the urethra is so small. Obstructions are often the result of plugs of inflammatory material, or small calculi or "stones" that have formed in the kidneys and have passed down into the bladder (see "Urolithiasis"). The cause of the inflammatory materials and stone formation it not well understood, though viral infections and diet may play a role.
Most affected cats are within 1 to 10 years of age. Initially cats may show signs of urinary tract inflammation, such as straining to urinate, frequent urination, blood in the urine, painful urination, or inappropriate urination (urinating somewhere other than the litter box). These bouts usually resolve in 5-7 days but will recur in many cats within 6-12 months. Once the cats become obstructed, they may attempt to urinate in the litter box but will produce no urine. They may cry, move restlessly, or hide because of discomfort, and eventually will lose their appetites and become lethargic. Complete obstruction can cause death of the cat in 3-6 days. A cat with a urethral obstruction will have a large bladder that is easily felt in the back half of the belly.
Cats that eat dry diets (and therefore get less water) or diets high in calcium, protein, or salt may be at an increased risk for developing calcium oxalate stones. Bladder inflammation leading to mucous plugs (sometimes called "Feline Urologic Syndrome" or "FUS") is more common in male cats. Congenital out-pouchings of the bladder ("vesicourachal diverticuli") can increase the risk of bladder infection, but they may also be a result of chronic inflammation.
In cats with signs of urinary tract inflammation, blood work is evaluated to check kidney function and to determine if there is any evidence of infection or other systemic illnesses. A urine sample is evaluated for crystals and may be sent in for culture, although bacterial infections of the bladder are uncommon in cats. In cats with recurrent infections, x-rays of the belly may be taken to see if calculi (stones) or other material are present in the kidneys or bladder (Figure 1), and the veterinarian may inject contrast material into the bladder during x-rays to see if there are any anatomic causes for straining and bloody urine, such as a bladder wall defect or a stricture (narrowing) of the urethra.
Clinical signs of straining and painful urinations can be seen in cats with bladder inflammation or calculi that do not have obstructions. Cats with constipation or anal sac disease may also strain and cry in the litter box.
Cats that have urinary obstruction require emergency treatment. The veterinarian will sedate or anesthetize the cat and place a catheter into the urethra to flush out the plug or force the stone into the bladder. The bladder is flushed through the catheter to remove any remaining sediment. The urinary catheter is then removed, and the cat is placed on intravenous fluids so that it will urinate frequently. Some cats require placement of a urinary catheter for 1-2 days until urethral swelling subsides; these cats may be placed on antibiotics. The veterinarian may also prescribe pain medication or other drugs to make the cat more comfortable and to help it relax.
In cats with calcium oxalate stones that have been flushed into the bladder, a cystotomy (surgical opening of the bladder) is performed to remove the stones (Figure 1) Cystotomy is also performed in cats with congenital outpouchings of the bladder ("vesicourachal divericuli").
Figure 1. Calculus ("stone") being removed from a cat's bladder.
If the obstruction recurs, a thorough work-up (including x-rays, cultures, and contrast studies of the bladder and urethra) should be performed before any surgery is considered (Figure 2, 3).
Figure 2. X-ray of a cat that had recurrent urinary tract obstructions for 6 months. A urinary catheter (yellow arrows) containing calcium crystals was found in the bladder (red arrows).
Figure 3. This urinary catheter had accidentally been left in a cat after its first bout of obstruction (the cat chewed the end of the catheter off, and the rest slipped inside the urethra and bladder). The cat obstructed multiple times until the catheter was removed surgically.
Cats that have 3 or more recurrences, that cannot be managed medically, and that do not have any underlying conditions that could cause recurrence may undergo perineal urethrostomy ("PU"), or surgical widening of the urethra (Figures
Figure 4. The cat's rear end has been prepped for surgery.
Figure 5. The surgical area is draped in.
Figure 6. The penis is dissected free from its attachments to the pelvis, and then will be opened to enlarge the urethra.
Figure 7. The new opening is completed.
When to seek referral
Cats that have strictures of the urethra, or high obstructions, are more difficult to correct surgically. Surgery in these cats should be performed by an ACVS Veterinary Surgeon. (Find a Surgeon)
Potential complications of surgery
After surgery, some cats will develop bleeding or swelling. Stricture (scarring and narrowing) of the urethrostomy site may occur if the cat traumatizes the surgery site or with incomplete dissection or urine leakage under the skin (Figure 8). Bacterial urinary tract infections occur in 25% of cats within the first year after perineal urethrostomy. Perineal urethrostomy does not prevent bladder inflammation or stone formation.
Figure 8. Because of incomplete dissection, this cat developed a stricture of the urethral opening (arrow). The cat had recurrent urinary tract infections and strained to urinate; these problems resolved once the urethrostomy was repaired properly.
Pelleted or paper litter may be used for several days after the surgery. Cats that have severe swelling or leakage of urine under the skin may require placement of a urinary catheter for 2-3 days (Figure 9). An Elizabethan collar is kept on the cat for 7-10 days after surgery to prevent self-trauma. In some cats, absorbable sutures are used in the surgery site, while other cats may have nonabsorbable sutures that require removal in 10-14 days. Cats should be rechecked 1, 3, 6 and 12 months after the surgery for urinary tract infections.
Figure 9. This cat had a high stricture or narrowing of the urethra, and had significant swelling after surgery. The bruising is from urine leakage under the skin. A urinary catheter was placed for 2 days, and the swelling resolved.
Prevention and prognosis
Prevention of urethral blockage depends on the cause of the blockage. If the surgery is performed properly, it is unlikely that cats will develop subsequent urinary obstructions. Perineal urethrostomy does not prevent bladder inflammation or stone formation, however, so clinical signs of urinary tract disease may continue in some cats.
—Dr. Karen Tobias, DVM, MS
Reviewed 10/1/2011 by Mitchell A. Robbins, DVM, Diplomate ACVS