Introduction
Most cats suffering from chronic renal failure (CRF) that has progressed to the point that the cat is exhibiting obvious clinical signs are severely ill. The most common diagnostic tools used to identify CRF, and to assess the health of the kidneys, are comprehensive blood tests, urinalysis and abdominal ultrasound.
Diagnosing Chronic Renal Failure in Cats
Laboratory Tests
Blood and urine tests can be used to detect CRF in cats at an early stage. Most veterinarians recommend that these tests be performed annually for cats 6 years of age and older. Blood work will identify the levels of blood urea nitrogen (BUN) and creatinine. BUN and creatinine are waste products that normally are eliminated by well-functioning kidneys. Elevated levels of these waste products in blood indicate declining kidney function. A full blood panel will also help eliminate or identify other causes of the cat’s clinical signs, such as diabetes or hyperthyroidism. Results of a urinalysis can identify a urinary tract infection, but also can measure the concentration of the cat’s urine. Cats in chronic renal failure usually drink large amounts of water and correspondingly urinate frequently as their body tries to flush excess waste products out of circulation through the kidneys into the urine. Reduced kidney function affects the kidneys’ ability to concentrate urine. Highly dilute urine can be a sign of chronic renal failure.
Ultrasonography
While many clinics do not have specialized ultrasound equipment, veterinarians may recommend an ultrasound in order to obtain an in-depth look at a cat’s kidneys when chronic renal failure is suspected. This procedure is painless and non-invasive, and the results can provide the veterinarian and the cat’s owner with critical information about the functional state of the animal’s kidneys.
Radiographs
Abdominal radiographs can demonstrate small or enlarged kidneys, which may have some bearing on the cat’s clinical signs and diagnosis.
Biopsy
Surgical biopsy can also be used in appropriate patients to identify the cause of renal failure. However, it typically is not done in most affected dogs and cats.