It is very common in veterinary practices — especially feline-only practices — for clients to present a cat with the problem of straining to urinate. Typically, the straining is often accompanied by other signs, such as urinating more frequently, urinating very small amounts, and doing it in inappropriate places, i.e. places other than the litter box.
In some cases, the owner will even report seeing blood in the urine. This combination of clinical signs is a syndrome that has been given several names over the years. The current favored term is feline lower urinary tract disease (FLUTD).
There are many possible causes of FLUTD, including bacterial urinary tract infections (UTIs), bladder stones, anatomic defects and even cancer.
In most cases, the FLUTD is “idiopathic” — a fancy way of saying that we can’t really figure out the cause. An important test to help determine the cause of FLUTD is a urinalysis (see related article in Catnip, March 2018). Urine specimens from cats with FLUTD may show a variety of abnormal findings, such as the presence of red blood cells, white blood cells, bacteria or crystals.
A few crystals in the urine may be considered normal, but an excessive number can lead to problems. Crystals may irritate the bladder, causing inflammation, which can lead to the constellation of clinical signs described above. Both males and females can be afflicted, but male cats are particularly at risk of developing a very dangerous consequence: urethral obstruction (UO).
Urethral obstruction
Obstruction of the urinary tract is a life-threatening disorder. It occurs when crystals in the urine coalesce to form sand. The sand combines with mucus and other inflammatory debris in the bladder, forming a plug in the urethra (the tube that leads from the bladder through the penis). This obstructs the flow of urine. Urine flow must be promptly restored or the cat will not survive.
Exactly why some male cats develop UO, while others do not, remains a mystery. Genetic and dietary factors are suspected. Indoor, overweight cats with a sedentary lifestyle are at increased risk for developing UO.
Don’t assume constipation
Cats with UO often show classic signs that include: frequent traveling in and out of the litter box, repeatedly squatting and straining to produce urine. The amount of urine passed may be very small — just a few drops — or there may be no urine produced at all. Some cats will cry or yowl during these attempts. Affected cats often groom their genital area excessively. It is clear that these cats are uncomfortable. Cat owners sometimes mistakenly interpret the unsuccessful attempts to urinate as a sign of constipation rather than urinary obstruction.
At my cat hospital, if a client calls and says that she thinks her cat is constipated, we immediately ask if the cat is a male. If so, we have the client bring in the cat immediately. Constipation is not usually an emergency, but urethral obstruction is — and in many of these cases, the “constipation” was indeed a misclassified urinary obstruction.
Male cats with signs of UO need to be evaluated by a veterinarian immediately. If your regular veterinary hospital is closed, the cat should promptly be taken to a 24-hour emergency center. Diagnosis of UO is usually made on physical examination; most cats with UO have a large, rock-hard distended bladder that can readily be felt in the abdomen.
Treatment of UO consists of sedating the cat and relieving the obstruction by placing a urinary catheter into the urethra. The bladder is then flushed multiple times with sterile fluid. Once the obstruction is relieved, a sample of the urine can be analyzed to obtain more information as to the possible cause of the obstruction. Blood can be collected while the cat is sedated to evaluate kidney function and electrolyte levels, and an intravenous catheter can be placed.
Serious electrolyte and acid-base derangements can develop during UO, and these must be corrected. This is accomplished by administering appropriate intravenous fluids. Pain medication may be prescribed to help with urinary discomfort. In general, the longer that the cat has been obstructed, the sicker he tends to feel.
Cats with long-standing obstructions (greater than 48 hours) may develop cardiac problems due to elevated levels of potassium in the bloodstream. An electrocardiogram (EKG) may be necessary to monitor the cat’s heart rate and rhythm. Cats with exceptionally high potassium levels may require medications immediately to rapidly lower the potassium level and prevent adverse effects on the heart.
Once the obstruction is relieved, the urinary catheter typically stays in place for 36 to 48 hours before it can be removed. The cat is then monitored very closely to ensure that he is able to urinate normally. The first 24 to 48 hours after the urinary catheter is removed is a critical period because this is the most likely time when the cat can re-obstruct. Once the cat is urinating normally, he can be sent home.
To minimize the chances of future recurrence of UO, cats should be encouraged to drink water. Obesity should be corrected or prevented. Prescription diets designed to prevent formation of urinary crystals should be fed for the rest of the cat’s life. Ideally, only the canned version of these foods should be fed, due to their higher water content.
Perineal urethrostomy
Although most cats never experience a second episode after preventive measures are taken, a few cats will suffer a recurrence. In these cats, a surgical procedure called a perineal urethrostomy (often referred to as a “PU”) may be recommended to prevent future episodes.
There is no real consensus regarding exactly when a PU should be considered. Factors include the frequency and severity of the obstructions, the owner’s perception about the cat’s quality of life and the cost. (In my experience, most owners will request the surgery on the third episode of obstruction.)
Perineal urethrostomy involves removal of the male external genitalia, resulting in a shorter, wider urethra. This may increase the incidence of future urinary tract infections, but greatly reduces the chance of another life-threatening urethral obstruction.
Urethral obstruction is a common, potentially life-threatening disorder encountered in male cats. Despite the severe metabolic consequences associated with UO, treatment usually results in a high success rate, with a survival rate higher than 90 percent. — Arnold Plotnick, DVM, DACVIM
