digestive system: feline urologic syndrome

The Classic Comprehensive Handbook of Cat Care




Feline urologic syndrome (FUS) is a term used by veterinarians to describe the signs caused by a number of disorders that affect the bladder and/or urethra of cats. Some veterinarians prefer to use the term feline lower urinary tract disease (LUTD) in place of FUS. Signs of lower urinary tract disease can be caused by inflammation of the bladder (cystitis) and/or urethra (urethritis), stone formation in the bladder (urolithiasis), and/or urethral obstruction.

Signs of cystitis most often include bloody urine and frequent urination of small amounts, sometimes accompanied by excessive licking at the genitals. Some affected cats display signs of discomfort when the abdomen is palpated (felt) in the bladder area. Cats with cystitis may also begin urine spraying. Inflammation of the urethra may accompany cystitis, or urethritis may occur by itself resulting in signs very similar to those of cystitis but unaccompanied by blood in the urine. Since some urine that contains blood does not look discolored to the naked eye complete urinalysis is necessary.

Urolithiasis occurs when hard stones form from mineral crystals found in the urine. The stones (urinary calculi, cystoliths) may range from very small sandlike grains to ones as big as large pebbles. Single or multiple stones may be present. These stones are irritating to the bladder itself thereby causing cystitis and the signs that typically accompany it. Bladder stones may be accompanied by stone formation in the kidneys. Veterinarians diagnose bladder stones by evaluating urinalyses, urine cultures, and X-ray and/or ultrasound studies of the urinary tract.

Small urinary stones, amorphous crystalline material (magnesium ammonium phosphate) mixed with mucoid secretions (struvite), or mucous alone may completely or partially block the urethra of cats, causing extreme difficulty or complete inability to urinate. This is an emergency and calls for immediate veterinary examination, since an unrelieved urinary obstruction can cause bladder rupture. Affected cats make repeated trips to the litter pan without producing any significant amounts of urine. Cases of complete urinary obstruction that go unnoticed or untreated progress until the cat becomes depressed, weakened, and dehydrated. Eventually, vomiting, total collapse, convulsions, coma and death will occur. Even if treated, cats with urinary obstruction in the later stages may not recover.

Systemic body changes caused by uremia (toxemia caused by excessive retention of wastes normally excreted by the kidneys) and kidney damage are sometimes irreversible.


Bacteria, diet, water intake, patterns of urination and activity, stress, and heredity all can play a role in producing and controlling signs of lower urinary tract disease. Viruses have been isolated from some cats with cystitis and/or urinary obstruction, and they may be the primary culprits in some cases of feline urologic syndrome. Cats with lower urinary tract disease may even have cancer of the bladder or urethra or an anatomical deformity in the area. Often more than one problem is present in a single cat with signs of feline urologic syndrome. In order to avoid recurrent signs of illness, it is important to determine exactly which factors are active in producing any individual cat’s signs. A cat who is exhibiting signs of FUS should always be evaluated by a veterinarian who can perform and interpret the diagnostic tests necessary to sort out the problems.

The majority of FUS cases with stone or plug formation are diet related, and some diets promote urinary crystal formation much more readily than others. The composition of a cat’s diet closely determines the urine pH (acidity or alkalinity). Some diets, notably those based on plant materials, tend to promote a more alkaline urine (urine pH higher than 7) than others, and alkaline urine is most favorable for the formation of crystals and uroliths. Mineral content of the diet, especially the quantity of magnesium present, also affects crystal formation. Vegetable materials used in the production of commercial cat foods have high magnesium content.

However, diets high in magnesium will not cause stone or plug formation if the urine pH is kept on the acid side (less than 6.5). Water intake and excretion associated with diet also can affect crystal formation since a reduced urine volume raises the relative mineral content of the urine, thereby providing a more favorable environment for crystal formation.

Reduced urine volume also discourages urination so urine is retained in the bladder, allowing more time for mineral crystalization. High-fat, energy- dense foods cause cats to excrete a greater proportion of water in their urine than in their bowel movements. Diets least likely to promote urolithiasis and urinary obstruction are high in fat and energy, easy to digest, low in magnesium, and produce an acid urine.

Good quality canned foods readily meet these criteria. Dry cat foods, on the other hand, have ingredients that contain relatively high magnesium levels and are less energy dense, causing more minerals to be consumed to meet the same caloric level. They are less digestible, which increases the amount of stool formed and the amount of fecal water excreted, thereby lessening urine volume. Dry foods also tend to promote alkaline urine unless they have been specially modified by the addition of acidifying agents. Only specially formulated dry foods are suitable for cats with the tendency to stone formation and/or urinary obstruction.


If you think your cat has signs of cystitis try to get a look at the urine and examine the cat thoroughly. Straining to urinate associated with cystitis can easily be confused with the straining accompanying constipation or severe diarrhea and vice versa, so you need to do something to try to determine exactly what the problem is. If your cat has been urinating in abnormal places such as a sink or the bathtub, it may be easy to see whether the urine looks blood tinged.

Otherwise a small urine sample can be obtained for home examination by placing an open plastic bag over the litter in the litter pan or by lining the litter pan with a fresh plastic bag and replacing the litter with nonabsorbent polystyrene foam bits. Blood-tinged urine almost always confirms the presence of severe bladder irritation and indicates that your cat should be examined by a veterinarian, who can perform a complete urinalysis and culture the urine to determine whether bacteria are present, and who can prescribe medication as needed. Bacteria that are isolated from cases of bladder inflammation and/or urinary obstruction in cats can be responsible for retrograde infection of the kidneys and permanent damage to the urinary system if they are not eliminated.

Cystitis may also be present when the urine looks normal to you. In this instance only a urinalysis will confirm the condition’s presence. You can present a fresh (less than thirty minutes old or kept refrigerated up to three hours) urine sample in a clean container to your veterinarian for analysis. Most veterinarians, however, prefer to obtain their own urine samples to avoid laboratory errors associated with old and/or contaminated specimens. Many veterinarians obtain the screening urinalysis sample in the office by a safe, relatively painless, and quick procedure called cystocentesis.

A fine needle attached to a syringe is passed through the abdominal wall and into the bladder, where a small sample of urine is withdrawn. This procedure avoids inconvenience for you as well as contamination of the urine sample that can confuse the interpretation of lab results.


If your cat shows signs of cystitis but you cannot be sure urine is being passed, immediate physical examination by you or your veterinarian is necessary to determine whether or not urinary obstruction is present.

Urinary obstruction is rare in females; their broad urethras are not easily plugged by sandy material. It almost always occurs in males (both castrated and uncastrated), whose narrow urethras become blocked quite easily. Knowing this may help you with diagnosis. Feel for the bladder. In obstructed cats, it can be felt as a lemon-sized or larger hard object, and the cat (unless very depressed) will usually react as if in pain. (Unobstructed cats with cystitis who have urine in their bladders often urinate when you feel for their bladders.) Look at the penis. It is often extended beyond the prepuce; if it isn’t visible, expose it. In obstructed males its tip is often bloody and/or bruised looking, and sometimes a bit of white, sandy material can be seen protruding from the urethra.


If you conclude that your cat is obstructed or cannot be sure that he isn’t, veterinary help is imperative to avoid bladder rupture. Only in instances of veterinary unavailability should you waste time attempting to relieve the obstruction yourself. If a veterinarian is absolutely not available, you can try the following.

  1. Use firm but gentle manipulation of the penis to try to squeeze the obstructing material from the urethra. Try rolling the penis between your fingers, working from nearest the body to the tip, and try milking the penis from its base to its tip. If your motions are being effective, gritty-feeling, white or blood-tinged material will be expressed like toothpaste from the end of the penis. If you relieve the obstruction completely, urine will usually begin to flow freely from the penis.
  2. If you remove some sandy material but urine doesn’t flow, then try squeezing the bladder gently (you can easily rupture it if you aren’t careful). This will sometimes result in a free-flowing stream of urine.

An obstruction relieved at home still requires veterinary care if at all possible. Acutely obstructed cats tend to become plugged again, and most cats docile enough to allow you to manipulate the penis and distended bladder are extremely ill and need the specialized supportive care only a veterinarian can give.

digestive-system-feline-urologic-syndrome-300x213 digestive system: feline urologic syndrome

Relieving Urinary Obstruction Veterinarians have many techniques for relieving obstruction. Unless the cat is extremely depressed, most veterinarians administer general anesthesia, and once the obstruction is relieved, a catheter (tube) may be sutured in place and left for a few hours or days to assure that the cat remains unblocked. Fluid therapy is administered to correct dehydration, stimulate a free urine flow, and to remove toxic wastes from the body.

Blood tests (to measure uremia) are often necessary. As in cats with uncomplicated cystitis, urinalysis will be performed and appropriate medications administered and dispensed for home use.

The most common drugs used in treatment of bladder inflammation and blockage are urinary acidifiers, antispasmodics, and antibiotics.
Antibiotics are useful only if bacteria are present in the urine and against the bacteria that invade the cat’s body secondary to the stress of the bladder problem. Antispasmodic drugs are used to relax the smooth muscle of the bladder and urethra in an attempt to prevent reobstruction and to provide relief from discomfort. Urinary acidifiers are drugs which, as their name suggests, help promote the production of urine with an acid pH instead of an alkaline one.

Although antispasmodics and antibiotics are usually discontinued as signs requiring them resolve, urinary acidifiers often are used on a long- term basis. A commonly used one is ammonium chloride that your veterinarian will supply or that you can purchase in pet supply stores.

Urinary acidification should be undertaken only under the instruction and monitoring of your veterinarian. Many commercial cat foods sold in pet store and supermarkets are already acidified and addition of ammonium chloride to these may cause problems. Excessive acidification can cause a potentially fatal metabolic acidosis, demineralization of bone, and low blood potassium levels (hypokalemia). Hypokalemia can result in profound muscle weakness, kidney damage, and death.


Measures other than urinary acidifiers designed to help prevent recurrent urinary problems all involve the management of your cat at home.

1. Be sure to encourage adequate water intake by providing fresh water freely available at all times. Water intake can be increased 50 to 100% by adding ordinary table salt to the cat’s food. A pinch is all that is necessary, but avoid using it if your cat is elderly or has a disease that may be associated with high blood pressure (e.g., heart or kidney problems), since increased salt intake may aggravate high blood pressure.

2. Feed a diet low in magnesium. Recommended diets contain no more than 20 milligrams magnesium per calorie (kcal) of diet consumed. This is about equivalent to 0.1% magnesium on a dry-matter basis.

3. Avoid dry foods unless they are specifically recommended for feeding to cats with urinary disease. Do not feed these special diets to cats without tendencies to urolithiasis since they may promote problems such as low blood potassium levels in cats who are especially sensitive to the effects of urinary acidification.

4. Provide a litter pan that is clean and dry at all times. Many cats are so fastidious that they will hold their urine rather than use a litter box they consider too soiled. This causes urinary stagnation that can contribute to crystal formation and urinary tract infection. Some cats will remain indoors for long periods of time to avoid going outside to urinate in inclement weather but will use a clean litter pan if one is provided.

5. Encourage activity in sedentary cats. Inactive cats tend to empty their bladders less often, resulting in urinary stagnation.

Even with the best home treatment, cats with cystitis and/or urolithiasis problems often have recurrent bouts of bladder inflammation or obstruction. It is impossible for your veterinarian to predict whether your cat’s condition will be a one-time problem or a recurrent nuisance.

Veterinarians can only confirm the condition and make sure no other complicating problems are present. Simple feline cystitis (unaccompanied by bladder infection, bladder stones, or tumors) in female cats is more of an inconvenience for you and your cat than a life-threatening medical problem, since recurrences usually cause only signs of bladder irritation.

Recurrent urinary obstruction in male cats, however, is a serious and life- threatening situation. A good alternative to constant worry over the threat of obstruction is a surgical procedure called a perineal urethrostomy. In this surgery the small urethra of the male is enlarged so it no longer easily becomes blocked.


Although this surgery cannot cure the underlying problem, performed by a good veterinary surgeon its success rate is high, and it solves the problem of worry and the repeated expense of treatment for urinary obstruction. Cats who have undergone perineal urethrostomy need periodic urinalysis since they are more susceptible to bacterial urinary tract infections than other cats.