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Chronic Kidney Disease in Cats

By Cynthia Minter, DVM
angell.org/generalmedicine
generalmedicine@angell.org
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One of the most common diseases of senior cats is chronic kidney disease (CKD). It goes by several names (chronic renal failure, renal insufficiency), but all refer to the same process: a progressive, irreversible decline in kidney function. In this disease, the kidneys lose their ability to appropriately regulate how much water is stored in the body versus how much is excreted in urine. As a result, urination becomes excessive, and your pet may drink more to compensate. Later in the course of the illness, certain electrolytes may become imbalanced, muscle mass and weight may decrease, a secondary anemia (low red blood cell count) may develop, and eventually symptoms such as decreased appetite, nausea, or vomiting may occur. While there is no cure for CKD, early diagnosis and intervention can slow its progression and keep your pet feeling better longer.

Even before symptoms appear, your veterinarian may note elevated blood kidney values on your senior cat’s annual blood tests. While CKD is one of the most common causes of these findings, there are a number of other causes, including dehydration, urinary tract obstruction, bladder or kidney infection, upper urinary tract stones, cancer of the kidneys, or a toxic plant or medication that was ingested. Your veterinarian will likely recommend additional testing to confirm that there is no other explanation for the elevated kidney values. These tests may include a urinalysis, bacterial urine culture, urine protein level (urine protein:creatinine ratio), abdominal imaging (x-rays or an ultrasound), or a new blood test to evaluate kidney function called a symmetric dimethylarginine (SDMA) level.

Once your veterinarian determines that your cat has chronic kidney disease, the next step is staging by the International Renal Interest Society (IRIS) guidelines, to find out how far the disease has progressed. This helps ensure that appropriate treatments are started at the right time. In addition to measuring the blood kidney values, staging involves measurement of a urine protein level (if protein is found in the urine), and a blood pressure measurement.

The first recommendation your veterinarian will probably make, regardless of how severe the changes to your pet’s kidneys are, is to stop any medication that may further damage the kidneys, such as non-steroidal anti-inflammatory drugs or certain types of potent antibiotics. Other medications may need adjustments in dose or frequency, so be sure to inform your veterinarian of all medications and supplements that your pet is taking. If your pet also has another condition, such as a urinary tract infection, urinary stones, or high blood pressure, these should be treated as they may be worsening your pet’s kidney function.

One of the first symptoms of CKD you may note in your pet is an increase in the frequency of drinking and urination. It is therefore very important, even in the very early stages of the disease, to ensure your pet has fresh, clean drinking water available at all times, ideally at multiple locations around the house. A switch to a canned food may also be beneficial to improve hydration. While it used to be that a prescription kidney diet was only considered later in the disease process, once blood kidney values become more substantially elevated, there is now evidence that cats with early CKD may benefit from eating a prescription diet that is formulated specifically for this stage. These diets are low in phosphorus but still maintain adequate levels of protein to support healthy weight and muscle in senior cats. They are only available with a prescription from your veterinarian, as they are not appropriate for cats without CKD. Whether to make a diet change is something that your veterinarian will determine based on blood and urine testing, taking into account any other conditions your pet may have that require a specific diet.

If your cat’s blood kidney values are more significantly elevated, your veterinarian will most likely recommend a change to a prescription kidney health diet that is restricted in both phosphorus and protein (unless your pet has concurrent medical conditions that make this diet unsuitable). Additionally, electrolytes such as phosphorus and potassium should be routinely monitored, and may require a medication to lower phosphorus levels (phosphorus binders) or a potassium supplement. The kidneys play an important role in stimulating the bone marrow to produce red blood cells, so as kidney function declines, anemia can develop. If the anemia becomes severe enough to cause symptoms such as lethargy or weakness, your veterinarian may recommend an injectable medication (given at home or in the veterinary clinic) to stimulate red blood cell production.

While every pet with any degree of CKD should have free access to water and ideally a diet that encourages water intake (such as a canned food diet), pets with significant kidney disease may reach a point where the water loss through urine exceeds the amount they can replenish by drinking or eating. These pets may benefit from fluid supplementation by injection under the skin, either daily or every few days. However, this treatment is not without its risks, and this decision must be carefully discussed with your veterinarian, taking into consideration any other health issues (such as heart disease) that your pet may have.

In the very advanced stages of CKD, you may notice a declining appetite, nausea, vomiting, weakness or lethargy. There are a number of medications that can improve your cat’s comfort and quality of life, including anti-nausea medications and appetite stimulants. The majority of these are safe for long-term use in cats with CKD, but it is important to ask your veterinarian about the appropriate dose and frequency, as cats with decreased kidney function may metabolize drugs differently.

While chronic kidney disease has no specific cure, there are many things that you and your veterinarian can do to improve your cat’s health and comfort. Maintaining a close relationship with your veterinarian throughout your pet’s senior years is important, making it possible to diagnose this condition early and take steps to slow its progression and reduce its effects on your pet’s quality of life.

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