Nutrition for Cats with Chronic Kidney Disease

My cat was diagnosed with chronic kidney disease. Why does she need special food?

Chronic kidney disease (CKD) is the most common kidney-based disease in older cats. Waste products from the body (compounds called creatinine and blood urea nitrogen) are normally filtered out of the blood by the kidneys and leave the body in the urine. In cats with CKD, the kidneys don’t function well and are unable to filter waste products, so those compounds build up in the bloodstream and result in one or more signs of illness, such as nausea, loss of appetite, lack of energy, or weight loss. For more information about CKD, see the handout "Chronic Kidney Disease in Cats".

There are four main goals for managing CKD in cats:

1. Control the clinical signs associated with the build-up of waste products in the blood.
2. Minimize problems with fluid and mineral balance.
3. Sustain adequate nutrition to keep the pet at a stable body weight.
4. Try to slow the progression of CKD.

Veterinary therapeutic diets have been designed for cats with CKD and are referred to as “kidney support” or “kidney friendly” products. They come in kibble, canned, and liquid forms. 

When compared to over-the-counter foods designed for healthy adult cats, a kidney support diet is formulated to deliver reduced levels of phosphorus, sodium, and protein. Kidney-support diets also have increased levels of potassium and omega-3 fatty acids. Research has shown that cats with CKD who eat a kidney-support diet are often better able to avoid a condition called metabolic acidosis, and slow the progression of CKD.

How do nutritional requirements differ for cats with CKD?

When kidneys are compromised with reduced function, they are not as effective at removing waste products from the body through the urine. The kidneys lose the ability to “concentrate” urine, so cats with CKD have “dilute” urine (not concentrated). To continue to remove waste products (toxins) while having more dilute urine, cats with CKD compensate by drinking more water. Therefore, it is critical to provide these cats with an unlimited supply of fresh, clean water every day.

To encourage more water intake, veterinarians often recommend changing the pet’s water several times daily and cleaning the water bowl daily. Canned pet foods are high in moisture, so using a canned kidney support food as the cat’s diet can also help improve water intake.

Limiting dietary phosphorus in cats with CKD appears to help delay disease progression. Phosphorus content in the diet is linked to protein content, so to achieve lower phosphorus levels, there must be some reduction in dietary protein. Among veterinary therapeutic diets, there are two forms of kidney support foods marketed for “early” or “advanced” kidney disease. Products labeled for early kidney disease have reduced phosphorus and moderately reduced protein, while products labeled for advanced kidney disease have slightly more restricted phosphorus.

Some protein reduction is needed to restrict phosphorus in a feline kidney diet, but if the cat’s protein intake is too low, its body will start to break down its own lean muscle mass. Finding the right balance can be challenging. For CKD cats with uremia, decreasing dietary protein helps alleviate clinical signs. Uremia occurs when creatinine and blood urea nitrogen build up in the bloodstream. When a cat with CKD develops uremia, you may observe bad breath, nausea, vomiting, absence of appetite, and ulcers in the mouth. Reduced dietary protein also means the kidneys don’t have to work as hard to filter the blood, which helps preserve kidney function.

"In cats with CKD, the kidneys lose their filtering capacity, 
and too much potassium gets lost in the urine."

Although there are no scientific studies showing the benefits of modified sodium content in diets of cats with CKD, it is believed that mild sodium restriction can reduce the workload on the kidneys, and this in turn helps to maintain a reasonable blood pressure.

Cats need potassium in their diet for many different reasons. When the kidneys are functioning normally, they actively retain the amount of potassium needed for health. In cats with CKD, the kidneys lose their filtering capacity, and too much potassium gets lost in the urine. The loss of potassium can worsen CKD, so an elevated level of potassium is included in kidney support diets.

Dietary omega-3 fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) help reduce the production of inflammatory compounds that create oxidative stress on diseased kidneys. When EPA and DHA are added to kidney support diets, they help slow the progression of CKD.

How can I make good nutritional choices for my cat with CKD?

Your veterinarian will help you choose an appropriate formulation for your cat. There are many commercial therapeutic diets marketed for “early” or “advanced” kidney disease; they are available as kibble, canned, and liquid diets. These products are designed to be palatable because it is important for cats with CKD to eat adequately and maintain a stable body weight and body condition. If needed, you can add water, tuna juice, or low-sodium broth to the food to improve its flavor and palatability.

Your veterinarian will help determine your cat’s daily food portion and may recommend regular weigh-ins and periodic evaluations to monitor blood and urine parameters.

Unfortunately, some cats lose interest in food as their kidney disease progresses. The challenge is to minimize food aversion as much as possible when patients are nauseous. Your veterinarian may prescribe medication to manage nausea or vomiting. If a cat is unable to meet daily energy requirements, a feeding tube can be used to deliver nutritional support, medications, or fluids.

Your veterinarian may discuss another option: a homemade diet. This is a good time to consult with an experienced veterinary nutritionist to ensure your cat receives the proper nutrition. Your veterinarian is your best resource for determining the nutritional approaches or options for your cat as CKD progresses.