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.
Hyperthyroidism in cats is almost always associated with a cancer-a benign adenoma (more
common) or a malignant adenocarcinoma. These cancers tend to occur in older
cats and the major effect is the increased thyroid hormone production they
stimulate. Exposure to secondhand cigarette smoke may be a factor. Himalayans
and Siamese have a lower risk for this problem.
The first signs may be dramatic. The increase in thyroid hormones tends to
cause an increase in appetite-the finicky eater now...
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
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.