Ronald S. Hines DVM PhD 9/14/07

This problem is sometimes called Feline Urological Syndrome (FUS) or Feline Lower Urinary Tract Disease (FLUTD) or FUS/FLUTD. This perplexing disease of the bladder and penis in males and bladder and urethra in females is still poorly understood. For reasons veterinarians do not understand, small sharp crystals form in the urine of these cats. The problem often begins when they are two to four years of age. Long hair, pure bred and run-of-the mill alley cats seem equally prone to this disease. Until recently, these sharp crystals composed exclusively of struvite (Magnesium Ammonium Phosphate). Within the last few years, the incidence of calcium oxalate crystals has mysteriously increased. This disease is never fatal to female cats but it is frequently life-threatening in male cats.

Until 1993, the vast majority of lower urinary tract disease was caused by deposits of sandy material called struvite. This material accumulated in the bladder. caused urethral irritiation in females and urethral obstructions in male cats. Struvite sand accumulated when the pH (acidity) of urine is greater than 7 and when dietary magnesium levels are high.. As animal nutritionists realized this, they reformulated cat foods to produce acid urine with a pH range of 6.3 to 6.7. This reformulation did lower the incidence of struvite crystals in house cats. However, it aparently made urine conditions optimal for the formation of calcium oxalate crystals. So today, struvite and oxalate crystals occur with equal frequency.

Much more about this disease remains unknown than known. Because male cats have narrower, longer urethras (the tube leading from the bladder to the penis), F.U.S. can be a life-threatening disease in male cats. Female cats with crystaluria are in obvious distress but because the urethra is shorter and wider, they never loose the ability to urinate. The typical scenario is a cat that is obviously uncomfortable. It spends long periods squatting in its litter box unable to pass more than a few drops of urine. The urine is often tinged with blood. Female cats are more likely to urinate in exotic locations such as the laundry basket or kitchen sink. In male cats, these tiny crystals cause the urethral tube to swell to a point where the cat can no longer pass urine. At this time, the cat becomes rapidly depressed as toxic metabolites accumulate in its blood. Male cats that are on the borderline of obstructing often have a whitish cheesy past on the tip of their penis. If you gently massage their abdomens, an orange sized object, the urinary bladder, can often be palpated. I call this disease the Garfield syndrome – it appears to be a disease of easy living. I have never seen it in a barn cat or in a large group of outdoor cats. It is usually a pampered fat indoor cat that breaks with the disease.

Because these urinary crystals are composed primarily of magnesium, one theory advanced by nutritionists was that the problem occurred due to feeding cat foods high in mineral (ash). This seemed logical. The only problem was that no one was able to produce the disease by feeding high ash diets. So other factors must be at work. Some speculated that a bacteria or virus caused the disease. However, most cats with this problem have no bacteria or virus in their urinary tracts. Another thought was that lethargic, indoor cats do not drink enough water. We know that these crystals occur more frequently in concentrated urine. However, just as high ash diets would not cause the disease, concentrated urine will not either.

One can identify a male cat that is at high risk of plugging up by the extremely narrow stream of urine passing through the penis. I almost never catheterize a blocked cat. I have found that the irritation caused by the catheter (particularly rigid Sherwood Sovereign catheters) quickly cause the cat to block a second time. With each succeeding blockage, the diameter of the urethra and damage to the bladder increases. I use gentle massage of the penis to break down the obstruction. When this is insufficient, I use a very subtle 20 gauge in intravenous catheter and irrigate the bladder with acetic acid and nitrofurazone solution using a technique called hydro propulsion. I then give the cat large doses of sodium bicarbonate to correct acid/base imbalances and up to 30ml per pound of subcutaneous lactated ringers solution to force the kidneys to naturally flush the crystals out the urethra. I send these cats home as quickly as I can because cats tend to be unhappy, stressed out patients. I have the owners continue to flush (diurese) the cat using soups and broths. Be sure none contain onion. A single Gerber’s strained baby beef with 6 empty jars of water all brought to a boil makes an excellent liquid. A turkey baster or 3 milliliter syringe makes an excellent dosing apparatus. I start the cat on Hills c/d diet or CNM’s UR diet. Home made diets can be found on my web page. If c/d diet is still to high in mineral to solve the problem, I place the cat on s/d diet at least until the cat has stabilized. Another perplexing element of this disease is that some cats will never experience the disease again despite whatever diet is fed to them; where as other cats will experience recurring bouts of the disease on the low ash diets. Since canned cat foods are up to 80% water, it is best to feed canned diets to cats that have experienced F.U.S. to produce maximum urine. Some veterinarians advocate the use of cat pheromones to reduce stress and anxiety – especially in multi-cat households. Others advocate placing the cat on amitriptyline (Elavil 2 to 12mg/cat) for the same effect.

Male cats that plug near the end of the urethra and have otherwise acceptable urine flow rates are candidates for a surgical procedure that removed the narrow portion of the urethra. The procedure is called a perianal urethrostomy.

The incidence of calcium oxalate sand or stone formation in cats seems to be rising in the United States. Unlike struvite, oxylate precipitates out of solution in an acid urine. So diets designed for struvite do not help. Sodium-potassium citrate supplementation of food shows potential in preventing oxalate reoccurence.

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