Kidney Failure (Uremia) Symptoms in Cats

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:

  • A blockage in the lower urinary tract associated with feline lower urinary tract disease (FLUTD) or a congenital bladder defect
  • 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 kidney insufficiency.
  • 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 certain parameters.

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 rapid decline.

Signs of uremia include apathy and sluggishness, loss of appetite and weight, dry haircoat, a brownish discoloration to the surface of the tongue, and ulcers on the gums and tongue. The breath may have an ammonialike odor. Vomiting, diarrhea, anemia, and episodes of gastrointestinal bleeding can occur. Eventually, the cat falls into a coma and dies.

Diagnosing kidney failure may require a number of techniques. X-rays, with or without dye studies, along with ultrasound evaluations, can be important. Blood work, especially blood chemistry panels that look for toxic waste levels in the blood, should be done. Many cats will show increased levels of BUN (blood urea nitrogen), creatinine, and phosphorus. Anemia will show up in cats with chronic renal failure.

A urinalysis will show if the kidneys can still filter and concentrate the urine. Looking at urine sediment may suggest a cause for the kidney failure. ERD-HealthScreen is an early detection test that looks for the protein albumin in the urine (microalbuminuria). It is hoped that with early detection and treatment, the progression of kidney failure can be slowed. However, many inflammatory conditions, such as gingivitis, may also cause microalbuminuria.

This article is excerpted from “Cat Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.