If you notice any signs of Chronic Kidney Disease (CKD) in your cat, you should visit your veterinarian immediately. The first step to formally diagnosing CKD is a thorough physical exam done by your veterinarian. They may find that your cat is dehydrated, has sores in their mouth, experiencing muscle loss as well as abnormalities in heart function, mentation, and blood pressure. Confirmation of CKD requires additional blood and urine testing to determine whether the kidney function is impaired and to rule out any other underlying medical problems.
How is CKD diagnosed?
Testing your cat’s levels of waste products in the blood can be indicative of how well the kidneys are functioning. Your veterinarian will look specifically at the circulating levels of blood urea nitrogen (BUN) and creatinine and when these values are high, they can be suggestive of kidney failure. Your veterinarian will also assess the blood levels of sodium, potassium, phosphorous, red blood cells, and proteins in order to diagnose CKD. The detection of symmetric dimethyl arginine (SDMA), a waste product of protein metabolism, is an early indicator of CKD and can be used in addition to the complete blood count and chemistry analysis.
Testing your cat’s urine for its color, pH, and presence of protein, blood, bacteria and other cells can also provide important information regarding the health of a cat’s kidneys. It is also important to culture a urine sample to rule out the possibility of bacterial infection of the urinary tract in suspected cases of CKD.
Other studies that can be useful in evaluating a cat with suspected CKD include imaging studies such as abdominal ultrasound, radiographs (X-rays), and, in some cases, microscopic evaluation of biopsy samples.
Given the potential for hypertension in cats with CKD, measurement of a cat’s blood pressure is also an important part of the medical evaluation for this disease.
Tests for Chronic Kidney Disease
If your cat has symptoms of CKD, your veterinarian may recommend some or all of the following tests to determine whether treatment is needed.
Symmetric dimethyl arginine (SDMA)
Blood urea nitrogen (BUN)
Electrolytes (including sodium and potassium)
Red blood cell count
Presence of red blood cells
Presence of other cells
Urine culture for bacteria
Microscopic evaluation of biopsy samples
What do the stages mean?
It’s important to realize that cats with early stage chronic kidney disease do not experience many of the signs and symptoms that are common in later stages. This is because nephrons in the kidneys have a large amount of reserve capacity and only need very little (~25%) functional nephrons, so by the time we see clinical disease, it means that over 75% of healthy tissue has been destroyed.
With regular wellness visits and annual blood testing, your veterinarian will be able to detect mild-moderate kidney damage where only 25-40% of the functioning nephrons have been lost due to CKD. Early detection is the key to improving your cat’s survival and quality of life as we have many options for intervention and even slowing down the progression of CKD.
Late stage CKD is defined as greater than 50% loss of functioning nephrons. Cats with late stage CKD may experience a buildup of the waste products and other compounds in the bloodstream that are normally removed or regulated by the kidneys. This accumulation may make them feel ill and appear lethargic, unkempt, and lose weight. They may also lose the ability to concentrate their urine appropriately, and as a result, they may urinate greater volumes and drink more water to compensate. The loss of important proteins and vitamins in their urine may contribute to abnormal metabolism and loss of appetite. They may also experience elevated blood pressure (hypertension), which can affect the function of a number of important systems, including the eyes, brain, and heart.
Another cause of lethargy in cats with CKD is the buildup of acids in their blood. The kidneys of cats with CKD may not excrete these compounds appropriately, making affected cats prone to blood acidification, or acidosis, a condition that can significantly affect the function of a variety of organ systems in the body. CKD may also decrease a cat’s ability to produce red blood cells, which can lead to anemia, a reduced concentration of red blood cells in their blood. This may cause their gums to appear pale pink, or in severe cases, whitish in color, and may make them lethargic.
What should I do if I suspect CKD in my cat?
Today cats with kidney disease can live a longer and healthier life thanks to improved dietary and drug therapies. You can play an important role in your cat's health by learning to recognize the warning signs of kidney disease. If you have an adult cat and have noticed these signs and symptoms, schedule an appointment with your cat’s veterinarian right away.