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Feline Lower Urinary Tract Disease

Feline lower urinary tract disease, also called feline urologic syndrome (FUS), is the most common disorder affecting the lower urinary tract in cats. The lower urinary tract is the urinary bladder, bladder sphincters, and urethra. Therefore, conditions affecting any of these organs can cause FLUTD. Cystitis, meaning inflammation of the bladder, is another term commonly used, but should be specifically reserved for conditions affecting only the urinary bladder.

Lower urinary tract problems are by far the major health concern of cat owners-although they do not occur in most cats. One reason is that FLUTD has a 50 to 70 percent rate of recurrence. Although FLUTD can occur in cats of all ages, it is seen most commonly in those older than 1 year. It occurs in both sexes, but the anatomy of the male increases the likelihood of bladder obstruction. It is more common in obese cats, possibly due to mechanical interference with voiding or to infrequent voiding in a less active cat.

The signs of FLUTD include prolonged squatting and straining; entering and leaving the litter box often, sometimes without voiding; frequent urination; passing bloody urine; urinating in unusual locations (possibly because the litter box becomes associated with pain); licking the penis or the vulva excessively; and crying out during the act of voiding.

FLUTD accounts for the great majority of feline urinary tract symptoms (dysuria, hematuria, and anuria), and although the signs of FLUTD might suggest a bladder or urethra infection, studies have shown that in most cases a bacterial infection is not present-at least not initially.

Causes of FLUTD

There are a number of important contributing factors that explain why some cats get FLUTD, but no one circumstance accounts for all cases. It is known that

  • FLUTD can be caused by the urethra being plugged by a pastelike, gritty, or sandy material composed primarily of mucus and struvite (magnesium-ammonium-phosphate) crystals, which are about the size of grains of salt. Although struvite crystals constitute a major part of most plugs, other types of crystals may be found. Some plugs are composed primarily of mucus, blood, and white cells.
  • FLUTD can also be related to uroliths-crystals or stones-found in the urinary tract. The type of urolith will vary depending on the cat's diet and urine pH factors. The two most common types are struvite (magnesium phosphate) and calcium oxalate. Factors influencing urolith formation in cats include concurrent bacterial infections; infrequent urination caused by a dirty litter box; reduced physical activity; and reduced water intake due to poor quality or no water available, or feeding exclusively dry cat food.
  • Cat urine is normally slightly acidic. Factors that favor an alkaline urine include the type of food eaten and the presence of bacterial urinary tract infection. Acid urine has antibacterial properties. Despite this observation, some cases of FLUTD occur in cats with acid urine. These cats may suffer from calcium oxalate uroliths. If the urolith occurs in the urethra, a life-threatening obstruction may occur.
  • Bacterial cystitis and urethritis (inflammation of the urethra) have long been accepted as basic causes. Current research indicates that bacteria are not involved in most cases, at least not at first. However, bacterial cystitis may be a very important cause of recurrent attacks. Also, keep in mind that the potential for infection increases with obstruction. Again, recurrent infections may be the result of antibiotic resistance, so the urine should be cultured before beginning any treatment.
  • Diet and water intake have been proposed as contributing factors. Cats who eat dry food take in less water with their meals and also lose more water in their stools. Presumably, dry cat food leads to a more concentrated urine and a greater amount of sediment. Cats who eat dry food exclusively do not urinate as frequently and therefore sediment and bacteria are not as effectively flushed from the urinary tract.
  • Stress also may play a role in sterile (negative bacterial culture) outbreaks. Signs of dysuria often flare up associated with emotional or physical upheavals in the household.

In summary, no one theory accounts for all cases of FLUTD. It does seem likely that reduced water intake, diets that contain large amounts of such crystal precursors as magnesium and calcium, urinary pH, as well as other currently unknown factors all contribute. Bacterial infection, once established, is an important cause of recurrent attacks.
