Written by: Judy Karnia, DVM
Chronic Kidney Disease (CKD) is the medical term for long-term changes in the kidneys leading to a decrease in their function. We may refer to it as kidney insufficiency or CRF, chronic renal failure. When I diagnose CKD in a patient, many of my clients become very concerned that their cats will not live much longer and ask about quality of life and how long they have left with their cat. This depends on the severity of the disease and how well it responds to treatment. Most cats live for years and have a good quality of life. By doing some medical testing, we can better determine the likely prognosis and what treatments are needed. The sooner in the course of the disease that we diagnose it, the better the cat will do. CKD is a progressive disease but we can slow the progression and keep your cat feeling good for a long period.
Stages of Chronic Kidney Disease
IRIS, the International Renal Interest Society, has developed a staging system from one to four to help with prognosis and treatment decisions. The stages are based on the level of creatinine in the blood with mild increases indicating stage one and high elevations indicating stage 4. Creatinine is a muscle enzyme that is excreted by the kidneys and builds up in the blood when kidney function decreases. It will increase with dehydration and decrease in very thin cats but your veterinarian will take these factors into account when staging your cat.
There are also substages based on blood pressure measurements and protein levels in the urine. Hypertension (high blood pressure) can occur in kidney disease and lead to damage to other organs. A urine sample can be sent to the lab to check the Urine Protein/Creatinine level. The worse the kidney function, the more protein will leak into the cat’s urine.
Testing for Kidney Disease in Cats
Other tests that can help determine the severity of the kidney disease and help with treatment decisions include blood tests, urinalysis, urine culture, radiographs (x-rays) and ultrasound. Besides the creatinine, the blood tests look at many other things. Blood urea nitrogen (BUN) gives us more information on the progression of the kidney disease and hydration level. CKD also can affect electrolyte and mineral levels, especially potassium, calcium, and phosphorus. We also watch the blood test results for signs of anemia or low protein levels.
The urinalysis shows us the concentration of the urine and indicates any infection. Cat urine is usually very concentrated but becomes dilute when the kidneys can no longer reabsorb water in their filtration process. Finding a low urine concentration shows that the high creatinine and BUN are due to kidney disease and not some other issue. Cats with CKD are more susceptible to bladder and kidney infections, which can be found with a urine culture.
Radiographs of the abdomen can help to see if there is any mineralization in the kidneys or any stones in the bladder or kidneys. It can also show other medical problems, such as arthritis that need to be treated. An ultrasound can show the structure of the kidneys and any possible mineralization, stones, or tumors.
Diagnosing CKD is only the first step. In some cats, unfortunately, the CKD is too far advanced for treatment to work. However, with proper diagnosis and treatment, most cats live for years with a good quality of life. Finding CKD in the early stages gives your cat the best possibility of this. Watch for subtle changes in your cat, such as changes in thirst, appetite, urination and behavior, and weight loss. Bring your cat into your veterinarian every six months for a complete exam and periodic blood tests.