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Feline Lower Urinary Tract Disease
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.
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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.
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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.
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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.
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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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