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In my cat specialty practice, one of the most common
scenarios I am faced with is the presentation of a cat that has been
straining to urinate. Accompanying the straining are often other signs,
such as urinating more frequently, urinating very small amounts, and
doing it in places other than the litterbox. Often times, the owner
will report seeing blood in the urine. The combination of some or all
of these clinical signs is a condition that has been given several names
over the years. The term “feline urologic syndrome” (FUS) was coined in
1970 to describe a disorder in cats characterized by abnormal urination,
obstruction of urine flow, bladder stones, and bloody urine.
Unfortunately, the term FUS was adopted as term that encompassed nearly
all lower urinary tract disorders in cats, regardless of cause, leading
to misdiagnoses and inappropriate treatments in a lot of cases.
Now, cases of
naturally occurring feline lower urinary tract disease (FLUTD) of
unknown cause are more properly classified as having “idiopathic” (cause
unknown) FLUTD (sometimes abbreviated “iFLUTD”).
Before a cat can be said to have idiopathic disease,
recognized causes of urinary tract disease must be eliminated, such as
bacterial, fungal, and parasitic urinary tract infections, bladder
stones, urethral plugs, anatomic defects involving the bladder or
urethra, and neoplasia (cancer). Many times, the exact cause of
clinical signs in cats with naturally occurring FLUTD defies
explanation. Approximately 55% - 64% of cases yield no specific cause,
and can be properly called iFLUTD.
Idiopathic FLUTD can be classified as obstructive, in which
a stone or a plug obstructs urine flow, and non-obstructive, in which
urine flow in maintained. Non-obstructive iFLUTD occurs in both male and
female cats of all ages, but young to middle aged cats are more commonly
affected, with the average age being 3 ½ years. Cats less than 1 year
old or more than 10 years old are rarely affected. The feline urinary
tract responds to disease in a limited number of ways regardless of the
disorder. As a result, straining to urinate, urinating small amounts,
with increased frequency, often in inappropriate places, with or without
obvious blood, is the typical scenario. In male cats, nonobstructive
iFLUTD often precedes the obstructive form the disease.
Most of the time, the results of bloodwork are normal in
cats with nonobstructive iFLUTD. Urinalysis results can be variable.
Sometimes, crystals are present in the urine. Crystals can irritate the
bladder lining, causing capillaries (tiny blood vessels) in the bladder
wall to bleed. Rarely, bacteria are present. Blood is commonly found,
either grossly, or microscopically. X-rays are usually normal, although
special dye studies may reveal a thickened, irregular bladder wall.
This is a result of chronic irritation. Occasionally, a bladder stone
or an anatomic defect is identified on x-rays.
Treatment of the condition can be very frustrating for the
veterinarian. If the urinalysis reveals the presence of bacteria, the
urine should be cultured, and antibiotics should be prescribed. If
crystals are present, an appropriate diet should be prescribed.
Struvite crystals (the most common) form in alkaline urine. A diet that
acidifies the urine should be prescribed. Calcium oxalate crystals form
in acid urine. An alkalinizing diet should be prescribed. Several
companies make prescription diets designed to address the problem of
crystals in the urine. Occasionally, a cat with struvite crystals, when
treated with an acidifying diet, will develop calcium oxalate crystals,
and vice versa. Some cats, oddly enough, will have both crystals
present in the urine simultaneously. Choosing an appropriate diet for
these cats can be frustrating.
The Royal Canin
company makes a diet (“Urinary SO”) that is designed for cats that are
prone to developing both types of crystals.
Rather than approach the crystal
problem by manipulating the pH, this diet causes the urine to become so
dilute that neither crystal can form. The diet does cause cats to
consume large quantities of water, and produce excessive amounts of
urine, so cat owners should be warned of this beforehand.
If x-rays reveal a bladder stone, surgery and medical
dissolution are the current treatment options. Struvite stones can be
dissolved using a special mineral-restricted diet. The diet is designed
to be fed on a temporary basis only; once the struvite stones are gone,
the cat is switched to a nutritionally complete diet that acidifies the
urine, preventing new struvite stones from forming. Calcium oxalate
stones, however, cannot be dissolved. They must be removed surgically.
Once removed, an alkalinizing diet is prescribed to prevent formation of
new oxalate stones.
The most difficult cases are those in which no obvious
cause for the urinary tract disease is present. Urinalysis reveals
adequately concentrated urine, with no bacteria and no crystals. Blood
in the urine is the only abnormality detected. X-rays are normal – no
bladder stones or anatomical defects are visible. As a veterinarian
specializing in cats, I find these cases to be the most challenging and
frustrating to treat.
Several years ago, it
was noted that some cats with iFLUTD had visible changes in the bladder
wall that were very similar in appearance to that seen in humans with a
condition called interstitial cystitis. The condition in humans is
characterized by frequent urination and lower abdominal pain, however,
urinalysis results appear normal. Amitriptyline, a tricyclic
antidepressant and anti-anxiety drug, has been used extensively in
humans for the treatment of interstitial cystitis. The drug also has
anti-histamine, anti-inflammatory, and analgesic properties. The exact
mechanism as to how it works in interstitial cystitis is unknown.
Because of its success in humans, there was some hope that amitriptyline
could provide symptomatic therapy for cats with iFLUTD. Initial studies
seemed promising, but subsequent studies proved the drug to be
ineffective, unfortunately.
Interestingly, a drug
that has recently gained widespread acceptance in the treatment of
arthritis in dogs and cats may hold the key to symptomatic therapy in
cats with iFLUTD. Glucosamine and chondroitin sulfate belong to a group
of substances called glycosaminoglycans (GAGs), compounds that serve as
the building blocks for cartilage. Available as nutritional
supplements, they are now routinely prescribed in dogs and cats with
arthritis, especially arthritis affecting the hip joints. It so happens
that the inside surface of the urinary tract is comprised of these same
GAGs that are present in cartilage. They help to create a water barrier
that protects the cells of the urinary tract, helping prevent bacteria
and crystals from adhering to their surface. Studies in humans with
interstitial cystitis suggest that damage to this protective layer may
be a causative factor in this disease, and some preliminary data suggest
that this layer may be altered in cats with iFLUTD as well. Although
some studies show no statistically significant effect compared to
placebo, a few individual cats in the treatment group did show dramatic
improvement when given this medication, and quickly relapsed when the
supplement was discontinued. Cosequin for Cats, (manufactured by
Nutramax Laboratories, Inc., Edgewood, Marlyand) is a glucosamine and
chondroitin sulfate preparation, available in tuna and chicken flavored
capsules. The contents of a capsule, when sprinkled onto a cat’s food,
is generally well-accepted by most cats. Veterinarians and clients
should realize, however, that this supplement, if it works, only serves
to make the cat more comfortable, and does not address the actual cause
of the bladder irritation, which in most cases, continues to remain a
mystery.
Updated 2/9/06 |
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