What Are the Stages of Kidney Disease in Cats?

Kidney disease is a common chronic condition in older cats. In order to characterize how advanced a cat’s kidney disease is, a universal scale, known as the IRIS guidelines, is used to measure their degree of illness. This scale is useful for both pet parents and veterinarians to help make decisions regarding treatment and prognosis.

It is important to remember that each cat is unique, and their kidney disease may not follow the exact path predicted by their stage of kidney disease. Many additional factors will influence their experience. Read on to learn all about this staging system and how vets manage chronic kidney disease.

What is cat kidney disease?

If your older kitty has recently been diagnosed with kidney disease, you are not alone. This is a common chronic condition, especially for cats over five years old.

In cats, chronic kidney disease is defined by a progressive loss of kidney function. This is different from acute kidney disease, where the kidneys are damaged suddenly by something like an infection or a toxin, and there is a possibility of a complete recovery. In chronic kidney disease, the kidneys gradually stop working as well as they used to. As a result, certain toxins are not flushed out of the body as well and other secondary changes occur.

Unfortunately, there is no cure for this kind of kidney disease. Many factors influence how long cats with kidney disease will survive. Some remain in the early stages of kidney disease for years without progressing, while others may decline more quickly. Most cats don’t show any signs of illness in the early stages of kidney disease and the only clue will be changes in their lab work. The good news is that when these early changes are detected, it gives you and your vet an opportunity to monitor your cat more closely, perform important follow-up tests, and craft an appropriate treatment plan. Cats in the early stages of kidney disease can live for many years, and it is a very manageable condition. 

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Stages of kidney failure in cats

Chronic kidney disease, also known as kidney failure, is characterized into stages based on lab findings. This system helps classify how advanced a cat’s kidney disease is, as well as other factors like prognosis and recommended treatments. The basic classification system is:  

• Stage one: This is the earliest stage of kidney disease in cats. These cats typically have no symptoms at all and show very mild changes in their lab work. The basic values used to measure kidney function, BUN and creatinine, are typically normal in these cats, however they may have other abnormalities like dilute urine, or protein in their urine.

• Stage two kidney disease in cats: Cats in stage two are often asymptomatic or have very mild signs like increased thirst or urination. These cats have mild increases in their BUN or creatinine along with other changes like dilute urine. 

• Stage three kidney disease in cats: This is where cats will develop more pronounced changes in their blood work with elevations in creatinine that are at least twice as high as normal. Cats in stage three are often subdivided into early and late stage three based on additional lab findings and the degree of their symptoms.

• Stage four kidney disease in cats: This is considered end stage kidney disease in cats. Stage four is characterized by a creatinine that is more than three times the normal value along with other abnormal lab findings. Cats in stage four kidney disease will have more severe signs of their disease and tend to have a shorter survival time. 

Cat kidney disease symptoms

The symptoms of kidney disease in cats will vary from one cat to the next, especially depending on how much their disease has progressed. Many signs of kidney disease overlap with other common diseases of older cats. It is very important to see a vet if your cat has any of these signs in order to determine the cause. Cats in the early stages of kidney disease often have no symptoms at all, while symptoms tend to get worse as their kidney disease advances. The common symptoms of kidney disease include: 

• Decreased appetite: As kidney disease advances, certain toxins build up in the body that can make cats feel nauseous and decrease their appetite.

• Increased urination: Kidney disease causes the urine to become more dilute as the kidneys lose their ability to reabsorb water. This leads them to void larger amounts of urine that is much more dilute.

• Increased thirst: As more water is lost through the urine and the kidneys become less efficient at reabsorbing water, cats are at risk of dehydration. They will experience increased thirst as their bodies try to replace the water that is lost.

• Vomiting: As certain toxins build up in their bodies, cats can experience nausea and vomiting. 

• Lethargy: Cats with advanced kidney disease are often lethargic for a number of reasons. They may become tired and weak as a result of their decreased appetite, dehydration, weight loss, or anemia (decreased red blood cell production). 

• Constipation: Dehydration and loss of water through the urine can also lead to constipation for some cats. 

• Weight loss: The combination of nausea and vomiting can lead to a decreased appetite and weight loss. A secondary problem with kidney disease can also be protein loss through the urine, which may also lead to decreased muscle mass and weight loss.

• High blood pressure: Cats with advanced kidney disease may develop high blood pressure. While there may not be any obvious signs of high blood pressure, some cats can develop secondary complications like sudden blindness, heart problems, or seizures.  

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Treatments by cat kidney disease stage

Routine veterinary care and check-ups every three to six months for older kitties are the most important ways to screen for kidney disease and determine the best treatment approach. Treatment plans will vary between cats depending on their specific symptoms and lab findings. Some basic guidelines include:

• Stage one kidney disease in cats: Perform additional screening measures to check for common complications like high blood pressure, protein in the urine, or high phosphorus. If these conditions are present, they will require treatment at this time. Additionally, take steps to keep your cat hydrated by providing a kitty water fountain, canned food, or mixing additional water into their diet.

• Stage two kidney disease in cats: Continue routine screening for complications like high blood pressure, protein in the urine, high phosphorus, or low potassium. If present, these conditions will require treatment. At this stage, consider a prescription kidney diet which has slightly lower protein and phosphorus than standard adult cat food. This may help to slow the progression of kidney disease for some cats. It is important to weigh this against your cat’s quality of life and pickiness. If you have a very finicky cat that won’t eat the kidney diet, it is more important that they eat consistently in order to stay hydrated, prevent weight loss, and continue to enjoy their life.

• Stage three kidney disease in cats: Cats in stage three kidney disease may also have more symptoms of their disease which require supportive care. In addition to the recommendations for stages one and two, cats at this stage may also need additional treatments to keep them hydrated and eating. This may include fluids given under the skin daily, known as subcutaneous fluids, as well as medications to reduce nausea and stimulate their appetite. 

• Stage four kidney disease in cats: Cats in stage four kidney disease often feel more sick than cats in the earlier stages of disease. They may need more frequent screening for complications like high blood pressure, high phosphorus, anemia, dehydration, or urinary tract infections. They will also need more supportive care to treat symptoms like nausea, dehydration, and decreased appetite.
  At this stage, it is very important to keep them comfortable and eating so it is best to offer them whatever they will eat and try a variety of foods. As cats in stage four kidney disease continue to decline, there may come a point where pet parents need to consider their cat’s quality of life and end-of-life decisions. It is important to discuss these matters as a family and with a veterinarian to help make the best choices for each individual cat.  

The bottom line:

• Chronic kidney disease is a common illness in older cats. 

• There is no cure for chronic kidney disease but there are treatments aimed at slowing its progression and keeping cats comfortable.

• Each cat’s experience is unique and not all cats progress at the same rate. Many cats can live for years with early stage kidney disease.

References

• “IRIS Staging of CKD” International Renal Interest Society. 2023. 

• Marino, C, et al. “Prevalence and classification of chronic kidney disease in cats randomly selected from four age groups and in cats recruited for degenerative joint disease studies.” Journal of Feline Medicine and Surgery, vol. 16, no. 6, 11 November 2013, pp. 465-472. 

• Schauf, S, et al. “Clinical progression of cats with early‐stage chronic kidney disease fed diets with varying protein and phosphorus contents and calcium to phosphorus ratios.” Journal of Veterinary Internal Medicine, vol. 35, no. 6, 21 September 2021, pp. 2797-2811. 

• Sparkes, A, et al. “ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease.” Journal of Feline Medicine and Surgery, vol. 18, no. 3, 2 March 2016, pp. 219-239.