Polycystic Kidney Disease in Cats: Causes, Symptoms, and Treatment

Polycystic kidney disease (PKD), or to give it its full name, autosomal dominant polycystic kidney disease (AD-PKD), is an inherited disease in cats that causes abnormal cysts (fluid filled sacs) to form in a cat’s kidneys.

These cysts are present from birth in affected cats, but initially they are so small that they don’t cause an issue. However, over time (usually several years) the cysts grow in both size and number, causing damage to the healthy tissue of the kidneys. This affects kidney function and can eventually lead to irreversible kidney failure.

The rate at which the disease progresses is very variable, with many cats not showing any symptoms until their more senior years, or at all. However, in other cases it can progress much more quickly, and even young cats can show signs of serious renal disease.

What Are the Symptoms of Polycystic Kidney Disease in Cats?

The cysts in the kidneys do not cause any symptoms until they are large enough to cause damage to the kidney tissue, affecting how the kidneys function. The average age this starts to happen is 7 years of age, but it can range from around 3 to 10 years of age.

Once the function of the kidneys is affected, the signs we see are the same as chronic kidney disease in cats. It isn’t possible to identify PKD as the underlying cause without performing further tests.

Clinical signs of kidney disease in cats include:

• Weight loss
• Increased drinking (polydipsia)
• Increased urinating (polyuria)
• Lethargy
• Poor appetite
• Poor coat
• Vomiting
• Diarrhea

These symptoms overlap with an array of conditions but a simple two-minute test can help you determine whether your cat’s kidneys might be involved. Click here to learn more about Kidney-Chek, an at-home saliva test that helps assess kidney function.

What Causes Polycystic Kidney Disease in Cats?

Polycystic kidney disease an inherited disease that is common in Persian cats and some other breeds.

Polycystic kidney disease is an inherited—or genetic—disease in cats, meaning it is passed on to them by their parents.  It is thought to be the most common inherited disease we see in cats, with around 6% of all cats being affected.

However, it is seen most frequently in Persian cats and related breeds, with some studies finding that nearly half of all Persian cats suffer from the condition.

Other breeds frequently affected include the Exotic Shorthair cats, British Shorthair cats, and to a lesser extent Ragdolls, Rex breeds, Himalayans, and Birmans.

Research has identified the mutated gene we think is responsible for causing the disease, called PKD1. Approximately 90% of cats carrying this mutated gene will have renal cysts within their lifetime.

A DNA test is available for cats and kittens that can check for the mutated PKD1 gene using a blood sample or cheek swab.

Cats who have been tested and found negative for the gene can be found on the AD-PKD Negative Register, allowing breeders and prospective new owners to check the status of the parents of potential new kittens. Since genetic testing has been available, the incidence of PKD in cats has been falling.

If you are interested in buying a kitten from a breed that commonly suffers from PKD (such as a Persian kitten), it is important to check that they are not carrying the mutated PKD1 gene. Your veterinarian will be able to discuss genetic testing with you.

How Do You Diagnose Polycystic Kidney Disease in Cats?

If you are worried your cat might have polycystic kidney disease, the first step is to take them to your veterinarian.

Your veterinarian will perform a full physical examination, including feeling the size and shape of your cat’s kidneys to check for abnormalities. They will also take a thorough history, including asking about your cat’s drinking, appetite, and urination.

The next step is usually comprehensive blood tests to assess your cat’s kidney function, in particular, urea and creatinine levels. Blood tests will also check for secondary effects of kidney disease, such as anemia. Your vet will also need to look at a sample of your cat’s urine to check for bacteria, protein, and white blood cells, and to assess if the urine is well concentrated.

However, to identify PKD as the cause of a kidney problem, your veterinarian will need to perform imaging. This is most commonly an ultrasound scan of your cat’s kidneys to look for the characteristic renal cysts found in PKD.

How Do You Treat Polycystic Kidney Disease in Cats?

Cats diagnosed with polycystic kidney disease need to eat a special kidney-support diet.

Unfortunately, there is no specific treatment for polycystic kidney disease in cats. As affected cats grow older, the cysts will increase in size and number. Currently there is no treatment available to stop or slow this process.

Treatment is the same as for chronic kidney disease in cats. One of the most effective treatments for supporting cats with kidney disease is a special prescription diet which has the best balance of phosphorous, protein, and salt to support their kidney function.

Depending on the results of further tests, your veterinarian may also recommend medications to reduce absorption of phosphorous from the diet, supplement potassium, and possibly tablets to lower your cat’s blood pressure if it is high.

As the disease progresses, palliative care, such as fluid therapy or anti-nausea medication, can really help your cat to feel as well as possible.

The rate at which PKD progresses is very variable in cats. Sadly, in cats who are very badly affected, the disease will eventually progress to cause renal failure. Your veterinarian can support you in assessing your cat’s quality of life and knowing when euthanasia might be the kindest decision.