Diseases of the lower urinary tract occur frequently in cats, affecting the bladder and/or the urethra (the tube that carries urine from the bladder to the outside of the body).
Most cats with lower urinary tract disease show remarkably similar signs, but to varying degrees. Cats will strain and make frequent and prolonged attempts to urinate, but usually the amount of urine passed during each attempt is quite small. Affected cats tend to lick their genital area excessively, and sometimes they will urinate outside the litter box, often preferring cool, smooth surfaces like a tile floor or a bathtub. Occasionally, there will be blood present in the urine.
Idiopathic Lower Urinary Tract Disease
Although cats with lower urinary tract disease behave in similar ways, the potential causes are multiple. Urinary tract infections (bacterial, fungal, parasitic, and perhaps viral), urinary stones, urethral plugs, cancer, and other disorders can affect the lower urinary tract of the cat. Unfortunately, in spite of extensive diagnostic tests, the cause of over half of the cases of feline lower urinary tract disease remains elusive; such disorders are called idiopathic feline lower urinary tract disease (IFLUTD). Cats suffering from IFLUTD make frequent attempts to urinate, probably as a result of bladder discomfort, and often are found to have blood in their urine. Dietary management (see below) has reduced the likelihood that cats with IFLUTD will develop a urethral obstruction, but there is no evidence that these "special" diets have reduced the incidence of idiopathic feline lower urinary tract disease itself.
Veterinarians have recently noted many similarities between this common form of feline lower urinary tract disease and a bladder disorder affecting humans called interstitial cystitis (IC). A psychologically stressful event often precedes the onset of lower urinary tract discomfort due to interstitial cystitis in humans. Interestingly, in one study, a recent weather change or a move to a new environment (both potentially stressful events to a cat) were factors related to the onset of signs related to IFLUTD.
A number of therapeutic methods have been attempted, but none are uniformly successful in the treatment of either IC in humans or IFLUTD in cats. Studies are ongoing to determine whether the human and the feline disorder are truly the same, and whether therapies helpful for humans will be of benefit to cats as well. Thankfully, most cases of IFLUTD resolve within a short period of time, even without treatment.
Urinary stones or uroliths can form in the urinary tract of cats and cause signs of lower urinary tract disease. Most of these stones are composed of either magnesium ammonium phosphate (also called struvite) or calcium oxalate. Most commercial feline diets are now formulated to reduce the likelihood of struvite formation by limiting the amount of dietary magnesium and by promoting the production of urine that is more acidic. In recent years, the percentage of stones composed of struvite has been decreasing, probably as a result of the feeding of such diets. Unfortunately, the percentage of stones composed of calcium oxalate has actually increased. The role, if any, that diet plays in the formation of calcium oxalate stones is actively being studied.
Management of a cat with uroliths is determined by the mineral composition of the stones. Surgical removal is usually required, although special diets designed to dissolve struvite uroliths are available from your veterinarian; if fed over a period of time, such diets are often successful. At this time, no such diets exist for the dissolution of uroliths composed of other mineral types. Regardless of the mineral composition of the stone, your veterinarian will design a medical plan (which may include dietary changes) to help prevent stones from redeveloping.
Urethral obstruction (when the cat's urethra becomes partly or totally blocked) is one of the most serious results of disease of the feline lower urinary tract. Male and neutered male cats are at greater risk for obstruction than females because their urethra is longer and narrower. Complete urethral obstruction or blockage is life threatening and requires immediate veterinary attention.
There are many causes of urethral obstruction in cats, but the two most common are uroliths and urethral plugs. Urethral plugs consist of a soft, compressible material that contains variable quantities of minerals, cells and cellular debris, and mucus-like protein. Many factors interact to produce uroliths and urethral plugs; viruses, bacteria, diet, decreased water consumption, physical inactivity, urine retention, stress, and urine pH may all contribute.
The most common mineral associated with urethral obstructions in cats is struvite. Previously, the ash content - and more recently, the magnesium content - of the diet was thought to be a primary cause of struvite formation in the urine. However, researchers have found that urine pH is a more important contributing factor; urine that is acidic provides a less favorable environment for the formation of struvite uroliths and crystals. It also was discovered that cats who are fed multiple small meals throughout the day, or who are allowed to eat their food free-choice, routinely tend to produce a more acidic urine - again less favorable for struvite formation - than cats fed only one or two large meals per day.
Mineral deposits also have a greater tendency to form in urine that is highly concentrated or that is retained in the bladder for long periods of time. To encourage adequate water consumption, and thus the formation of urine that is more dilute, fresh water should be available to cats at all times. Fastidious cats sometimes avoid using a dirty litter pan, so owners should provide clean litter boxes to encourage regular and frequent urination.
SIGNS OF URETHRAL OBSTRUCTION
A cat experiencing a urethral obstruction behaves similarly to any other cat with lower urinary tract disease: straining to urinate, frequently attempting to urinate, and producing little, if any, urine. However, as time passes, an obstructed cat typically becomes much more distressed - often crying out in pain. Frequently, owners think that the cat is constipated, when actually the cat is obstructed. The male cat may constantly lick at his penis, and the penis may be protruded. Small sand-like particle s are often seen around the penis.
Urethral obstruction is a true medical emergency; any cat suspected of suffering from this condition must be seen immediately by a veterinarian. When the urethra is completely blocked, the kidneys are no longer able to remove toxins from the blood and maintain a proper balance of fluids and electrolytes in the body. If the obstruction is not relieved, the cat will eventually lose consciousness and die. Death most frequently occurs as a result of electrolyte imbalances, which ultimately cause heart failure. The time from complete obstruction until death may be less than twenty-four to forty-eight hours. Immediate treatment is essential.
Catheterization (passage of a narrow tube up the urethra) usually relieves the obstruction, but other procedures are sometimes necessary. Unless the cat is comatose, catheterization usually requires sedation or anesthesia. After the obstruction has been relieved, treatment varies depending upon the condition of the cat. Dehydration and electrolyte imbalance are treated with intravenous fluid therapy. Antimicrobial medications are frequently given to combat bacteria, and drugs that help restore bladder function are sometimes required.
Hospitalization may range from a few days to several weeks, depending on the severity and duration of the obstruction. Some cats don't survive because treatment is initiated too late. For cats recovering from a urethral obstruction, the first few weeks after hospital discharge are usually the most troublesome because relapses are most common during that period of time.
For cats who continue to experience urethral obstruction in spite of proper medical management, a surgery called a perineal urethrostomy is often suggested. Cats that have undergone the procedure may still suffer bouts of bladder disease, however, they usually will not suffer from the life-threatening urinary obstructions that previously occurred.
Side effects of surgery can include bleeding for up to ten days after surgery, narrowing at the surgical site, urinary incontinence, and a greater incidence of other kinds of bladder diseases. For these reasons, perineal urethrostomy is usually considered to be a last resort.
A few unfortunate cats who have suffered from lower urinary tract disease will experience frequent recurrences of bladder inflammation, re-obstruction, or formation of uroliths. Fortunately, most others rarely experience the problem again or will have only occasional recurrences.
Home care of cats who have suffered from lower urinary tract disease is determined by the cause, and varies depending on the cat's condition and history. Usually dietary recommendations will be made, especially if struvite formation is of concern. Current feeding recommendations for the prevention of struvite urolith formation are as follows:
Feed diets that promote the formation of urine that is acidic. Most commercial diets currently available meet this criteria. Avoid supplementing such diets with additional urinary acidifiers, because over-acidification can cause metabolic acidosis, impaired kidney function, and mineral imbalance.
Restrict dietary magnesium intake to 40 milligrams per 100 kilocalories if acidic urine (pH of 6.4 or less) is maintained. Again, most commercial diets meet this criteria.
Feed small meals on a frequent basis or feed free-choice dry foods.
Provide clean, fresh water at all times.
Provide an adequate number of litter boxes (usually one more than the number of cats in the household), and keep them clean.