Feline Lower Urinary Tract Disease-FLUTD

FUS was the first name by which I knew the illness: Feline Urologic Syndrome.

FLUTD took its place a number of years ago. Feline Lower Urinary Tract Disease.

As you might imagine, a disease process about which even the experts can’t agree on a name is a very complicated syndrome. Pour yourself a large cup of coffee, and let’s dive into it.

Cystitis is a broad term meaning inflammation of a bladder, regardless of cause. If it refers to the gall bladder, it is cholecystitis. If it refers to the tiny container that holds tears where the upper and lower tear ducts meet, it is dacryocystitis. Today, however, we are discussing the urinary bladder.

The typical signs of this disease process begin with the same things one would expect to see with any source of bladder wall inflammation:

  • frequent urination (pollakiuria)
  • urinating small amounts
  • blood in the urine
  • straining to urinate
  • urinating in inappropriate locations
  • abdominal pain

Like dogs and people, cats can have bladder wall inflammation from the most common cause, bacterial infection. In uncomplicated cases these patients respond to treatment and clear up nicely. Because these patients frequently have pollakiuria, and arrive at our offices with empty bladders, we are forced to treat symptomatically. With no urine to test, we assume that they have bacterial infections when, in fact, sometimes they don’t.

With any cause of bladder wall inflammation the victim has an extreme urge to empty the bladder. In people, the result is frequent trips to the bathroom. Dogs may ask to “go out” often. Cats may make frequent trips to the litterbox. Dogs and cats alike may have “accidents,” and urinate in places they usually wouldn’t. Interestingly, cats often pick substrates like white sinks and tubs, or white bed linens, where discolored urine is more likely to be observed by owners. While it is difficult to give them credit for having that sort of mental capability, it happens often enough to be identified as a very interesting phenomenon.

Bacterial infections of the urinary tract can have complicating factors.

Stones may form in the bladder, with the most common ones being struvite and calcium oxalate. While people more commonly form stones in the kidneys, dogs and cats form stones there much less often. Stones in the bladder can cause mechanical bladder wall inflammation by their very presence. These stones often have rough outer surfaces that can abrade such tender tissues. That abrasion can lead to blood in the urine, even in the absence of infection.

Stones often abet bacterial urinary infections by “holding” infection in their crevices and layers. Even after periods of extended antibiotic therapy, infections may relapse because the antibiotic cannot penetrate the inner layers of the inanimate stone. As soon as bacterial numbers rise again, clinical signs recur.

Bladder wall irregularities can also cause recurrent bacterial infections of the urinary tract. Stones may cause scar tissue. Cancer may interrupt the normal function of the bladder wall. Persistent urachus, a physical abnormality that can remain from the fetus, leaves a pocket-shaped defect in the bladder in which bacteria can hide.

Conditions which we commonly treat symptomatically in cats as urinary tract infections (UTIs) are, in fact, something else.

The most common form of non-infectious cystitis (though infection may soon arrive as a secondary problem) is crystal irritation.

Decades ago, in the days of “FUS,” it was thought that there were only two forms of feline bladder inflammation: bacterial infection (with or without complications such as stones and bladder wall defects) and irritation from crystals formed by ingredients in the food that become concentrated in the urine.

Modifications were made in food formulations to minimize amounts of ammonium, phosphate and magnesium ions in the urine. When these three ingredients are present in alkaline, or high-pH, urine, they solidify to form struvite: crystals. In small numbers these crystals cause little problem, but in higher concentrations their spicules can irritate the bladder lining. If sufficient crystals are present, stones can form.

In male cats an even more ominous situation may present itself. Unlike female cats, the male cat urethra has a rapid and extreme taper, like a funnel, ending in a tiny opening. Even small numbers of crystals can quickly clog the distal end of the urethra, preventing the cat from urinating. Soon, toxic waste that should have been eliminated with the urine builds up in the bloodstream and uremic poisoning results. This condition is a life-threatening medical emergency. In the worst cases the bladder may become so enlarged that it ruptures, spilling its toxic contents into the abdomen.

Researchers soon learned that acidifying the urine was a useful weapon against struvite. The crystals appear in alkaline urine, but in low-pH urine they dissolve into solution, causing no problems. Thus, a combination approach of reducing the building blocks in a cat’s diet, combined with acidifying the urine is an effective technique.

Encouraging water intake by feeding canned food and/or adding water to the food helps to dilute the urine, reducing specific gravity and diluting any crystals that may form.

One must be careful, however, to not change the pH too much, because a too-acid urine predisposes the cat to calcium oxalate stones.

Hill’s Prescription Diet c/d, available in canned and dry forms, is excellent for holding that balance.

When it became clear that all cats’ bladder problems were not solved by diet alone, experts in feline urology began performing histopathology of affected cats’ bladders, and discovered that some suffer from a condition similar to interstitial cystitis in women. Fortunately, in cats, the disease usually responds to one or more of a variety of antiinflammatory drugs. Some feline patients do best on an anti-anxiety medication.

For reasons not fully understood, many of the cats in this latter category improve when antibiotics are administered, even in cases where neither urinalysis nor urine bacterial culture and sensitivity prove the presence of bacteria. One theory is that, because this is a cyclic condition with a waxing and waning course, the cat was going to get better on its own about the same time.

One aspect we understand for sure: most of these kitties are spared a lot of suffering with appropriate treatment.

If your cat experiences repeated problems relating to the urinary tract, now you understand that it may not be “simple” UTI. Be comforted by knowing that your pet’s doctor  now has the tools necessary to help these cats, regardless of the cause.


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