Most cats that are feeling and showing symptoms of chronic renal failure (CRF) are very sick and already have lost about 70% of their kidney function. The veterinarian will be presented with an older cat who “ain’t doin’ right” (called “ADR” in veterinary lingo). Any aging cat that is progressively weak and lethargic, losing weight and body condition, and drinking a lot and urinating a lot probably will be suspected of being in end-stage chronic renal failure. The veterinarian will take a complete history from the cat’s owner and perform a thorough physical examination. The initial evaluation will also include drawing blood and urine samples for routine analysis. The results of these tests will identify the levels of circulating waste products that healthy kidneys would normally filter out, such as blood urea nitrogen (BUN), phosphorus and creatinine. Consistently elevated levels of these substances in blood reflect declining kidney function. A blood panel can also help identify or eliminate other causes of the cat’s clinical signs, such as anemia, diabetes or hyperthyroidism.
Most veterinarians recommend that routine blood work (a complete blood count and serum biochemistry profile) and a urinalysis be performed yearly on cats after 7 years of age. A urinalysis is a simple diagnostic tool that can provide a great deal of information about a cat’s kidney function and overall health. The results of a urinalysis can identify a urinary tract infection and can show the concentration of the cat’s urine. Cats in chronic renal failure usually drink lots of water and urinate frequently, because their body is trying to flush out accumulating waste products. Cats with CRF have very dilute urine. A thyroid panel (run on a blood sample) can help to rule out hyperthyroidism in aging cats. Hyperthyroidism can exist apart from or in conjunction with renal failure, and if present may affect the treatment options. The veterinarian will also check the cat’s blood pressure, which often is elevated in cats with CRF. When chronic renal failure is suspected, the veterinarian may recommend an abdominal ultrasound to look at the cat’s kidneys. This procedure is painless and non-invasive, and the results can provide a tremendous amount of information about the kidneys’ functional status. Ultrasonography also may disclose other abnormalities. Abdominal radiographs (X-rays) can disclose abnormally small or enlarged kidneys, which often are associated with CRF. These procedures can also help identify kidney or ureter stones (nephroliths, ureteroliths), tumors, cysts or other causes of physical obstruction.
The veterinarian can take surgical biopsies of the cat’s kidneys and submit the samples to a laboratory to identify the extent of kidney damage. However, kidney biopsies are not routinely taken in cats, unless their kidneys are enlarged (renomegaly) or cancer – especially lymphoma – is suspected.
It is important to diagnose chronic renal failure promptly. Unfortunately, it can’t be cured. Treatment options are limited to managing the cat’s symptoms and trying to delay progression of the disease.