Many cat owners have experienced the frustration of the cat that can't urinate properly. These cats may be unable to urinate at all because of a complete obstruction of the urinary tract or may be straining frequently to urinate only to pass just a few drops of urine at a time, often with blood in it. All cats exhibiting signs of difficult urination should be examined by a veterinarian. Cats with a complete obstruction need to be treated immediately as urinary obstruction is a medical emergency that can result in death if left untreated.
Unobstructed cats will present with basically the same signs. Though not obstructed, they are usually quite uncomfortable. An examination and appropriate diagnostics are necessary to find the underlying cause and to direct appropriate treatment strategies. There are several causes of urinary problems in cats, some more easily diagnosed and treated than others. The syndrome of difficult urination in cats is known by several names, most commonly Feline Lower Urinary Tract Disease (FLUTD) and Feline Urologic Syndrome (FUS). These names refer to the syndrome of difficult urination, but not to a specific cause. Examination and diagnostics are necessary to find the specific cause in individual cats.
Cats exhibiting difficulty in urinating need to be examined. As mentioned above, cats with a complete obstruction of the urinary tract have a medical emergency and need immediate attention. An obstructed cat is diagnosed primarily based on the feel of the urinary bladder on physical examination. In a non-obstructed cat, the bladder is usually small and empty of urine. Obstructed cats will have a distended, painful bladder, may be vomiting and are always in need of immediate care. Obstructed cats build up toxins in there bloodstream that are normally eliminated through the urine. This results in an internal poisoning that is fatal if left untreated. Further, while rare, a severely distended bladder may rupture on its own, leading to the leakage of urine into the abdominal cavity. This causes a severe problem called peritonitis, also a life-threatening problem.
Based on physical examination and a history of what the cat is doing at home, the doctor will recommend diagnostic testing. Usually, the first step in the diagnostic process is a urinalysis. A complete urinalysis involves checking for the presence of bacterial, crystals, blood cells and other substances in the urine as well as measuring the concentration and pH of the urine. All this information gives the doctor clues as to the underlying cause of the cat's problem. Sometimes a urinalysis is the only diagnostic tool needed to solve the problem. Other times, the doctor may recommend a urine culture, abdominal ultrasound, or radiographs to more clearly define the problem. In some cases, an exploratory surgery is indicated to obtain a biopsy of the bladder wall or to remove bladder stones, if present.
Put in its simplest terms, cats that are straining to urinate are usually suffering from cystitis, inflammation of the urinary bladder. Cats with inflamed bladders, regardless of the cause of the inflammation, feel the urge to urinate as a result of irritation. They try to relieve that irritation by urinating frequently,often outside of the litterbox. Because they urinate so frequently, the bladder remains almost empty. Therefore the cat urinates only a few drops at a time. If the urethra, the tube leading from the bladder to the outside of the cat, becomes completely blocked, the straining cat will not urinate at all.
The bladder can become inflamed as a result of several different problems. In dogs and people, the most common cause of cystitis is a bacterial urinary tract infection. Because people are usually familiar with bladder infections, they often bring their straining cats in expecting them to be treated with antibiotic therapy. While cats can develop a bacterial cystitis, it is much more common for them to experience other causes of cystitis. Therefore, cats presented showing signs of cystitis need a diagnostic workup to determine the underlying cause. Simply treating these cats with antibiotics without a diagnostic workup may seem to result in improvement of the condition, but the signs usually return because the underlying cause is still present.
Common causes of cystitis in cats include crystal formation in the bladder and a condition most commonly called Feline Interstitial Cystitis. Less common causes include bladder stones, drug reactions, and tumors. Each of these causes will be discussed separately.
Sometimes crystals will form in the bladder of cats. While these crystals are microscopic, they have very sharp edges which rub on and cause irritation to the walls of the bladder. This leads to inflammation, irritation, and often blood in the urine. Affected cats will show the typical signs of cystitis--frequent urination with little passed, often with blood. If large numbers of crystals are present, a "plug" of crystals may get stuck in the urethra, causing complete obstruction and the inability to urinate. This is always a medical emergency. Cats use urine to rid themselves of waste products. If they cannot urinate, these waste products build up, leading to an internal poisoning of the cat. Untreated obstructed cats will continue to strain, often becoming vocal as the bladder distends and becomes larger and larger. They will stop eating, start to vomit, and eventually be too sick to get up. Death will occur if the obstruction is not relieved and the effects of the toxin build-up treated. This is why all cats showing signs of cystitis should be examined by a veterinarian--owners typically cannot differentiate between obstructed and non-obstructed cats until the obstructed cats become very ill.
Cats can form several different types of crystals. Longterm control to prevent crystal formation is usually dietary, with the type of diet being determined by the type of crystal present. The most common crystal is the struvite crystal, also known as the triple phosphate crystal or the magnesium ammonium phosphate crystal. We used to think that this type of crystal formed as the result of high ash content in the food. We now know that multiple factors lead to struvite crystal formation including the pH of the urine, the amount of magnesium and phosphorus excreted in the urine, the length of time urine stays in the bladder before the cat urinates, and the concentration of the urine. Foods formulated to prevent struvite crystal formation produce an acid urine, have lower levels of magnesium and ash, have higher salt content to encourage more drinking which leads to more dilute urine and more frequent urination. The bladder is emptied more quickly so crystals have less time to form. Many over-the-counter cat foods are formulated to prevent struvite crystal formation, but some severely affected cats need a more restricted prescription diet. Some cats will continue to form crystal despite our best efforts. Struvite crystalluria is diagnosed via a urinalysis.
The second most common type of crystal that cats form are calcium oxylate crystals. These are less common than struvite crystals, but some breeds, such as Himilayan cats, have a hereditary predisposition to forming oxylate crystals. Ironically, the factors which contribute to oxylate crystal formation are opposite of those which lead to struvite formation. Foods designed to decrease oxylate formation produce an alkaline pH urine rather than an acid pH needed to prevent struvite formation. That is why a urinalysis is so important. If a cat with oxylate crystals is treated for presumptive struvite crystals with a special diet, the struvite diet will actually cause more oxylate crystals to form.
Cats can form other crystals as well, but this is extremely rare.Sometimes crystals can congregate to form stones. Cats with stones will show the same signs as cats with crystals but are at greater risk of complete blockage. Due to their anatomy, male cats are more prone to complete blockages than females. If a cat forms struvite stones, it may be possible to dissolve those stones with a prescription diet fed for several weeks. Calcium oxylate stones are not dissolvable and usually require surgical removal in male cats. If the stones are small enough, a female cat may be able to pass them. Stones can be diagnosed via radiographs, ultrasound, or both.
Sometimes stones can be felt in the bladder on physical exam.Some cats will develop cystitis with no apparent underlying cause. These cats will usually have a normal urinalysis or a urinalysis that shows blood in the urine, but no crystals and no evidence of a bacterial infection. Urine culture is negative. Radiographs and ultrasound may show a thickened bladder wall but no crystals, no stones, and no evidence of tumors. These cats probably have feline interstitial cystitis, also known as sterile hemorrhagic cystitis. This condition is highly frustrating because there is no known treatment. These cats will usually exhibit signs on a cyclical basis. They usually show signs for three to ten days, then get better. Re-currence is common, but the frequency of episodes is highly variable from cat to cat and very difficult to predict.
Owners always want to do something to help the cat, often insisting on antibiotic therapy. When the cat gets better after starting antibiotics, the owner assumes the antibiotics cleared up an undiagnosed infection. In reality, the syndrome simply ran its usual course of spontaneous remission. But many owners remain convinced that the antibiotics help and may spend unnecessary money on repeated courses over the years. Antibiotic therapy should be reserved for cats with a confirmed bacterial cystitis (diagnosed via urinalysis and/or culture of the urine) and for cats at high risk of developing bacterial cystitis as a result of urinary catheterization to relieve a urethral obstruction. Even then, antibiotics should be given when the catheter is removed, not when it is placed, to prevent encouraging resistent bacteria.
There is one therapy that may improve interstitial cystitis in cats. While not yet proven effective, early studies are encouraging. This therapy involves supplementing cats with a product containing glycosaminoglycans, an important component of the normal protective lining of the bladder. The theory is that cats with interstitial cystitis have a disrupted glycosaminoglycans layer in the bladder. Without this protective layer, the bladder wall is subject to damage done by contact with urine, which can be highly irritating. Cats receiving glycosaminoglycans supplements may suffer fewer, less severe episodes of cystitis. This supplement is available in a capsule that can be opened and sprinkled on the food. Most cats will eat this supplement when added to food.
Another therapy that has been tried is antiinflammatory doses of steriods. While we used to feel that this therapy helped some cats, we now realize that these cats probably would have gotten better on their own in about the same time frame. Recent studies suggest that steriods have no benefit in this condition.
Hopefully, this section will help owners understand the complexity of Feline Lower Urinary Tract Disease and the frustration often involved in the diagnosis and treatment, especially in those cats suffering from Feline Interstitial Cystitis. If you have any questions concerning your individual cat, please discuss it with one of the doctors at uvma.