Kidney failure in cats 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 KIDNEY FAILURE IN CATS
Causes of acute kidney failure in cats include the following:
- A blockage in the lower urinary tract associated with feline lower urinary tract disease 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 in cats 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.
SIGNS OF KIDNEY FAILURE IN CATS
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.
DIAGNOSIS OF KIDNEY FAILURE IN CATS
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.
TREATMENT FOR KIDNEY FAILURE IN CATS
The outlook for a cat with kidney failure depends on a number of factors. Your veterinarian may want to make an exact diagnosis by ordering special tests to determine whether the disease is potentially reversible. A renal biopsy may be needed to determine the exact cause of the problem.
Acute kidney failure can be reversed if the underlying cause can be corrected before it permanently damages the nephrons. If the insult is severe, hemodialysis (more commonly called dialysis) may be necessary to try to give the kidneys a chance to heal. Dialysis is most commonly used short term to treat acute renal failure or toxicities, or while a search is conducted for a transplant candidate. Dialysis is extremely expensive, can only be done at a few veterinary referral centers, and still requires extensive medical management of the cat in addition to the dialysis sessions.
Most cases of chronic kidney failure occur in cats who have sustained irreversible damage to the kidneys. However, these cats may still have many happy months or years of life ahead, with proper treatment. It is extremely important to be sure these cats take in enough water to compensate for their large urine output. A supply of fresh, clean water should be available at all times (learn more…). Many cats will need supplemental fluids, given either intravenously at the veterinary hospital or subcutaneously at home.
The diet of a uremic cat should include protein of high quality, but lower in total amount, to minimize the amount of phosphorus and nitrogen that must be excreted by the kidneys. Special diets are available through your veterinarian. Canned foods are better than dry foods, because the canned food adds fluid to the diet.
Phosphorous restriction in the diet is important, although phosphate binders, such as aluminum hydroxide salt (Amphogel) can also be given. Vetoquinol has produced a veterinary product called Epakitin that is a palatable powder that also binds phosphates. However, this product also contains calcium, which may be contraindicated in the later stages of renal failure.
Large amounts of B vitamins are lost in the urine of uremic cats. These losses should be replaced by giving vitamin B supplements. Sodium bicarbonate tablets may be indicated to correct an acid-base imbalance. Potassium may also need to be supplemented. The kidneys are also important in the production of vitamin D. Cats in chronic renal failure may benefit from the addition of calcitriol to their therapeutic regimen. Your veterinarian may need to order special compounded versions of calcitriol to get the appropriate dosage for a cat.
Vomiting may need to be controlled with medications such as famotidine, ranitidine, omeprazole, or others, until the renal condition is stabilized.
Erythropoietin may be used to help counteract the anemia associated with long-term renal failure. Currently, human recombinant erythropoietin is used, which may lead to immune-based destruction of red blood cells and a renewal of the anemia over time. Research is continuing for a safe feline alternative.
Cats with hypertension will need therapy to lower their blood pressure.
A uremic cat who becomes ill, dehydrated, or fails to drink enough water may suddenly decompensate; this is known as a uremic crisis. The cat should be hospitalized and rehydrated with appropriate intravenous fluids and balanced electrolyte solutions.
Some exercise is good for a uremic cat, but stressful activity should be avoided.