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Diseases of the lower urinary tract
occur frequently in cats, affecting the bladder and/or the
urethra (the tube that carries urine from the bladder to the
outside of the body). Most cats with lower urinary tract disease
show remarkably similar signs, but to varying degrees. Cats will
strain and make frequent and prolonged attempts to urinate, but
usually the amount of urine passed during each attempt is quite
small. Affected cats tend to lick their genital area excessively,
and sometimes they will urinate outside the litter box, often
preferring cool, smooth surfaces like a tile floor or a bathtub.
Occasionally, there will be blood present in the urine.
Idiopathic
Lower Urinary Tract Disease
Although cats with lower urinary tract disease behave in similar
ways, the potential causes are multiple. Urinary tract infections
(bacterial, fungal, parasitic, and perhaps viral), urinary
stones, urethral plugs, cancer, and other disorders can affect
the lower urinary tract of the cat. Unfortunately, in spite of
extensive diagnostic tests, the cause of over half of the cases
of feline lower urinary tract disease remains elusive; such
disorders are called idiopathic feline lower urinary tract
disease (IFLUTD). Cats suffering from IFLUTD make frequent
attempts to urinate, probably as a result of bladder discomfort,
and often are found to have blood in their urine. Dietary
management (see below) has reduced the likelihood that cats with
IFLUTD will develop a urethral obstruction, but there is no
evidence that these "special" diets have reduced the incidence of
idiopathic feline lower urinary tract disease itself.
Veterinarians have recently noted many
similarities between this common form of feline lower urinary
tract disease and a bladder disorder affecting humans called
interstitial cystitis (IC). A psychologically stressful event
often precedes the onset of lower urinary tract discomfort due to
interstitial cystitis in humans. Interestingly, in one study, a
recent weather change or a move to a new environment—both
potentially stressful events to a cat—were factors related to the
onset of signs related to IFLUTD.
A number of therapeutic methods have been
attempted, but none are uniformly successful in the treatment of
either IC in humans or IFLUTD in cats. Studies are ongoing to
determine whether the human and the feline disorder are truly the
same, and whether therapies helpful for humans will be of benefit
to cats as well. Thankfully, most cases of IFLUTD resolve within
a short period of time, even without treatment.
Urinary
Stones
Urinary stones or uroliths can form in the urinary tract of cats
and cause signs of lower urinary tract disease. Most of these
stones are composed of either magnesium ammonium phosphate (also
called struvite) or calcium oxalate. Most
commercial feline diets are now formulated to reduce the
likelihood of struvite formation by limiting the amount of
dietary magnesium and by promoting the production of urine that
is more acidic. In recent years, the percentage of stones
composed of struvite has been decreasing, probably as a result of
the feeding of such diets. Unfortunately, the percentage of
stones composed of calcium oxalate has actually increased. The
role, if any, that diet plays in the formation of calcium oxalate
stones is actively being studied.
Management of a cat with uroliths is determined
by the mineral composition of the stones. Surgical removal is
usually required, although special diets designed to dissolve
struvite uroliths are available from your veterinarian; if fed
over a period of time, such diets are often successful. At this
time, no such diets exist for the dissolution of uroliths
composed of other mineral types. Regardless of the mineral
composition of the stone, your veterinarian will design a medical
plan—which may include dietary changes—to help prevent stones
from redeveloping.
Urethral
Obstruction
Urethral obstruction—when the cat's urethra becomes partly or
totally blocked—is one of the most serious results of disease of
the feline lower urinary tract. Male and neutered male cats are
at greater risk for obstruction than females because their
urethra is longer and narrower. Complete urethral obstruction or
blockage is life threatening and requires immediate veterinary
attention.
CAUSES
There are many causes of urethral obstruction in cats, but the
two most common are uroliths and urethral plugs. Urethral plugs
consist of a soft, compressible material that contains variable
quantities of minerals, cells and cellular debris, and
mucus-like protein. Many factors interact to produce uroliths
and urethral plugs; viruses, bacteria, diet, decreased water
consumption, physical inactivity, urine retention, stress, and
urine pH may all contribute.
The most common mineral associated with
urethral obstructions in cats is struvite. Previously, the ash
content—and more recently, the magnesium content—of the diet
was thought to be a primary cause of struvite formation in the
urine. However, researchers have found that urine pH is a more
important contributing factor; urine that is acidic provides a
less favorable environment for the formation of struvite
uroliths and crystals. It also was discovered that cats who are
fed multiple small meals throughout the day, or who are allowed
to eat their food free-choice, routinely tend to produce a more
acidic urine—again less favorable for struvite formation—than
cats fed only one or two large meals per day.
Mineral deposits also have a greater tendency
to form in urine that is highly concentrated or that is
retained in the bladder for long periods of time. To encourage
adequate water consumption, and thus the formation of urine
that is more dilute, fresh water should be available to cats at
all times. Fastidious cats sometimes avoid using a dirty litter
pan, so owners should provide clean litter boxes to encourage
regular and frequent urination.
SIGNS OF
URETHRAL OBSTRUCTION
A cat experiencing a urethral obstruction behaves similarly to
any other cat with lower urinary tract disease: straining to
urinate, frequently attempting to urinate, and producing
little, if any, urine. However, as time passes, an obstructed
cat typically becomes much more distressed—often crying out in
pain. Frequently, owners think that the cat is constipated,
when actually the cat is obstructed. The male cat may
constantly lick at his penis, and the penis may be protruded.
Small sand-like particle s are often seen around the penis.
Urethral obstruction
is a true medical emergency; any cat suspected of suffering
from this condition must be seen immediately by a veterinarian.
When the urethra is completely blocked, the kidneys are no
longer able to remove toxins from the blood and maintain a
proper balance of fluids and electrolytes in the body.
If the obstruction is not relieved,
the cat will eventually lose consciousness and die.
Death most frequently occurs as a result of electrolyte
imbalances, which ultimately cause heart failure. The time from
complete obstruction until death may be less than twenty-four
to forty-eight hours. Immediate treatment is essential.
MEDICAL
TREATMENT
Catheterization (passage of a narrow tube up the urethra)
usually relieves the obstruction, but other procedures are
sometimes necessary. Unless the cat is comatose,
catheterization usually requires sedation or anesthesia. After
the obstruction has been relieved, treatment varies depending
upon the condition of the cat. Dehydration and electrolyte
imbalance are treated with intravenous fluid therapy.
Antimicrobial medications are frequently given to combat
bacteria, and drugs that help restore bladder function are
sometimes required.
Hospitalization may range from a few days to
several weeks, depending on the severity and duration of the
obstruction. Some cats don't survive because treatment is
initiated too late. For cats recovering from a urethral
obstruction, the first few weeks after hospital discharge are
usually the most troublesome because relapses are most common
during that period of time.
SURGICAL
TREATMENT
For cats who continue to experience urethral obstruction in
spite of proper medical management, a surgery called a perineal
urethrostomy is often suggested. Cats that have undergone the
procedure may still suffer bouts of bladder disease, however,
they usually will not suffer from the life-threatening urinary
obstructions that previously occurred.
Side effects of surgery can include bleeding
for up to ten days after surgery, narrowing at the surgical
site, urinary incontinence, and a greater incidence of other
kinds of bladder diseases. For these reasons, perineal
urethrostomy is usually considered to be a last resort.
Prognosis
A few unfortunate cats who have suffered from lower urinary tract
disease will experience frequent recurrences of bladder
inflammation, re-obstruction, or formation of uroliths.
Fortunately, most others rarely experience the problem again or
will have only occasional recurrences.
Home Care
Home care of cats who have suffered from lower urinary tract
disease is determined by the cause, and varies depending on the
cat's condition and history. Usually dietary recommendations will
be made, especially if struvite formation is of concern. Current
feeding recommendations for the prevention of struvite urolith
formation are as follows:
- Feed diets that promote the formation of
urine that is acidic. Most commercial diets currently available
meet this criteria. Avoid supplementing such diets with
additional urinary acidifiers, because over-acidification can
cause metabolic acidosis, impaired kidney function, and mineral
imbalance.
- Restrict dietary magnesium intake to 40
milligrams per 100 kilocalories if acidic urine (pH of 6.4 or
less) is maintained. Again, most commercial diets meet this
criteria.
- Feed small meals on a frequent basis or feed
free-choice dry foods.
- Provide clean, fresh water at all times.
- Provide an adequate number of litter boxes
(usually one more than the number of cats in the household),
and keep them clean.
Prepared by the Cornell Feline Health
Center, Cornell University, College of Veterinary Medicine,
Ithaca, New York 14853-6401. The ultimate purpose of the Feline
Health Center is to improve the health of cats by developing
methods to prevent or cure feline diseases and by providing
continuing education to veterinarians and cat owners. Much of
that work is made possible by the financial support of friends.
©1997 by Cornell University. All rights reserved. Cornell
University is an equal opportunity, affirmative action educator
and employer. |
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