Kidney failure is the inability
of the kidneys to remove waste products from the blood. The buildup of toxic
wastes produces the signs and symptoms of uremic poisoning. Kidney failure can
come on acutely or occur gradually over weeks or months. Chronic renal failure
is a leading cause of death in pet cats.
Causes of acute kidney failure include the following:
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A blockage in the lower urinary tract associated with feline lower urinary
tract disease (FLUTD) or a congenital bladder
Trauma to the abdomen, especially when accompanied by pelvic fracture and
rupture of the bladder or urethra
Shock, when due to sudden blood loss or rapid dehydration
Arterial thromboembolism (a blood clot
blocking the artery), particularly when both renal arteries are obstructed
Heart failure, when associated with a persistently low blood pressure and
reduced blood flow to the kidneys
Poisoning, especially from ingesting antifreeze or Easter lilies
Causes of chronic kidney failure include these:
Nephritis and nephrosis, in which case the failure is usually of the renal
tubules, not the glomeruli.
Infectious diseases, especially feline infectious peritonitis and feline leukemia.
The use of nonsteroidal anti-inflammatory drugs (NSAIDs), especially during
periods of hypotension (low blood pressure such as occurs during anesthesia).
Various toxins. Antibiotics that are poisonous to the kidneys when
given for prolonged periods or in high doses include polymyxin B, gentamicin,
amphotericin B, and kanamycin. The heavy metals mercury, lead, and thallium are
also toxic to the kidneys.
Most elderly cats, if they live long enough, will have some degree of
Chronic renal failure and hyperthyroidism seem to often
go hand in hand, since they are both geriatric diseases. Treatment of
hyperthyroidism may unmask underlying chronic renal failure.
Cats with kidney diseases do not begin to show signs of uremia until about
70 percent of their nephrons are destroyed. Thus, a considerable amount of
damage occurs before any signs are noted. The degree of renal failure can be
determined by looking at laboratory data and tracking the progression of
One of the first signs of kidney failure is an increase in the frequency of
voiding. Because the cat is voiding frequently, it might be assumed that her
kidneys are functioning properly. Actually, the kidneys are no longer able to
conserve water efficiently. Cats will go to the litter box several times a day
and may also begin to urinate outside the box, since the box is getting dirty
faster. This large urine output must be compensated for by increased fluid
intake, and the cat will drink a lot more than usual. Also, because the urine
is dilute (not concentrated), bacterial infections of the bladder and kidneys
are much more common.
As renal function continues to deteriorate, the cat begins to retain
ammonia, nitrogen, acids, and other waste products in the bloodstream and
tissues (uremic poisoning). Blood chemistries will determine the exact levels
of these metabolic products. Cats in the later stages of kidney failure may
produce less urine than normal and, eventually, no urine at all, which leads to