Chronic Renal Failure
History. You examine a 15-year-old male Siamese cat. The owner reports that her cat is listless, inappetent, and thin. The cat has been drinking more water than usual lately, urinating large volumes, and vomiting frequently.
Clinical Examination. The cat is very thin and moderately dehydrated. The mucous membranes are pale. Both kidneys are easily palpable and feel small, firm, and slightly irregular. The hematocrit is 22% (normal, 30%-42%), serum creatinine level is 8.7 mg/dL (normal, 0.5-1.2 mg∕dL), and urine specific gravity is 1.012. The urine sediment is unremarkable.
Comment. The cat has chronic renal failure, which is seen frequently in geriatric patients in small animal practice. The serum creatinine level is elevated because progressive loss of glomerular function has severely reduced the GFR, and creatinine is not cleared from the plasma normally. The urine is not concentrated in response to dehydration because tubular function is also compromised. The smallness of the kidneys is an indication of chronicity and is a result of gradual nephron loss and scarring. Anemia is common in chronic renal failure and results from many factors, including decreased production of erythropoietin by the kidney.
Treatment. In veterinary medicine the treatment of chronic renal failure is usually supportive and symptomatic. This cat would probably benefit initially from rehydration with intravenous fluids and correction of electrolyte and acidbase disturbances as dictated by the serum chemistry profile. Chronic support may greatly improve the cat’s quality of life and slow the progression of disease. This should include a diet containing low total protein that is high in bioavailability, low sodium, and low phosphorus. Supplementing with the watersoluble vitamins may be beneficial. Anabolic steroids may help improve the anemia, although exogenous erythropoietin has become standard treatment in humans with anemia caused by chronic renal failure and is now being used in veterinary medicine as well.