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 urinary stones). 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 1-10 years of age. Initially cats may show signs of urinary tract inflammation, including:
- straining to urinate
- frequent urination
- blood in the urine
- painful urination
- 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 your primary care 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.
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. An Elizabethan collar is kept on the cat for 10-14 days after surgery to prevent self-trauma. In some cats, absorbable sutures are used in the surgery site, while other cats may have non-absorbable sutures that require removal in 10-14 days. Cats should be rechecked at 1, 3, 6 and 12 months after the surgery for urinary tract infections.
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 3). 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, so clinical signs of urinary tract disease may continue in some cats.
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.