Polycystic Kidney Disease in Cats

What is polycystic kidney disease?

Polycystic kidney disease (PKD) is a hereditary kidney disease that causes multiple cysts (pockets of fluid) to form in the kidneys. These cysts are present from birth. Initially, they are very small, but they grow larger over time and may eventually disrupt kidney function, resulting in kidney failure. Cysts may also develop in other organs, particularly the liver and pancreas. Some affected cats may also develop cardiac abnormalities.

What causes PKD?

PKD is an inherited condition. Cats that receive a defective copy of the gene from either one of their parents may show signs of PKD (autosomal dominant inheritance). Both males and females can be affected. 

All cats with the PKD gene, even those with only a few small cysts or those with no clinical signs, will pass the genetic defect onto their kittens, even if mated with an unaffected, healthy cat. It should also be noted that some cats with PKD have been found to be negative for PKD gene mutation, so there may be other mutations that cause PKD in cats.

Persian cats have the highest incidence of PKD. Studies have shown that the disease affects around one-third of Persian cats. Breeds developed using Persian bloodlines (e.g., Himalayan, Scottish Fold, British Shorthair, Chartreux, Exotic Shorthair, Burmilla, and Siberian Neva Masquerade) are commonly affected as well. In most other cats, especially mixed breeds, the condition is rare.

What are the signs of PKD?

Affected cats may present typical signs of renal failure, including:

• Drinking and urinating more than usual
• Anorexia (not eating)
• Weight loss
• Lethargy
• Nausea and vomiting

How is PKD diagnosed?

The diagnosis is based on breed, medical history, clinical signs, blood and urine tests, genetic testing, and ultrasound evaluation of the kidneys. Special radiographic dye studies may also be used in certain situations.

• Blood tests: Blood tests in later stages of the PKD will reveal increased levels of waste products normally eliminated by the kidneys, possible anemia (low numbers of red blood cells), and electrolyte abnormalities. 
• Urinalysis: An examination of the cat’s urine will likely reflect renal dysfunction (inability to properly concentrate their urine, protein in the urine, abnormal cells in the urine sediment). 
• Radiographs (X-rays) may show an irregularly shaped, enlarged kidney, although cysts cannot be seen on X-rays.
• Ultrasound examination is the best imaging tool for this condition, as the cysts are visible even from an early age, well before any signs of renal failure might develop.

How is PKD treated?

There is no specific treatment for PKD. Cats with PKD are treated the same as cats with any other form of chronic kidney disease. Treatments may include a therapeutic diet, fluid therapy, and medication to manage the effects of chronic kidney disease. Periodic recheck examinations and follow-up diagnostic testing are recommended to monitor the progress of the disease, allowing for appropriate treatment modifications.

What is the prognosis for cats with PKD?

Cats vary significantly in how rapidly cysts develop and renal failure progresses. In most cats, the cysts enlarge slowly and affected cats do not show signs of kidney disease until later in life, typically around seven years of age. In some cats, kidney failure occurs at a much younger age, while in others it does not develop at all. There is currently no way to predict how quickly the disease will progress in a particular cat.

What should I do if I am interested in purchasing a kitten with Persian bloodlines?

If you are interested in purchasing a Persian kitten or one with a Persian genetic background, it is important to verify that it is not carrying the PKD gene through genetic testing, available through several companies. Consult your veterinarian for details about this testing.