Polycystic Kidney Disease in Dogs

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 early in life. As the dog ages, these cysts gradually increase in size and number, replacing normal, functioning kidney tissue and disrupting kidney function. Over time, affected dogs develop signs of chronic kidney disease. PKD is common in cats, but uncommon in dogs.

What causes PKD?

PKD is an inherited condition. Dogs 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 dogs 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 dog. PKD is most diagnosed in Bull Terriers. Other predisposed breeds include Cairn Terriers and West Highland White Terriers.

What are the signs of PKD?

In young dogs, PKD is typically asymptomatic (has no symptoms), although not always. As dogs age, kidney function decreases as the functional kidney is gradually displaced by cysts. The clinical signs of PKD are often first observed in mature, middle-aged dogs. Signs of kidney disease are variable, and may include:

• Drinking or urinating more than usual
• Decreased appetite
• Weight loss
• Lethargy
• Nausea, vomiting, or diarrhea 

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.

• Physical examination: Your veterinarian will begin by performing a physical exam. In some cases, your veterinarian may be able to detect enlarged or irregular kidneys by feeling the abdomen. 
• Blood tests: These tests typically include a complete blood cell count (CBC) and serum biochemistry. Blood tests may reveal increased levels of waste products normally eliminated by the kidneys, possible anemia (low numbers of red blood cells), and electrolyte abnormalities. Your dog’s serum biochemistry will likely show elevations in three indicators of kidney function: BUN (blood urea nitrogen), creatinine, and SDMA (symmetric dimethylarginine).
• Urinalysis: An examination of the dog’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.

Additional diagnostic tests may include specific genetic testing, ultrasound-guided aspiration of a cyst to evaluate its contents and culture to check for infection, histopathology (examining kidney tissue under a microscope), and computed tomography (CT scan).

How is PKD treated?

There is no specific treatment for PKD. Dogs with PKD are treated the same as dogs 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 dogs with PKD?

Dogs vary significantly in how rapidly cysts develop and renal failure progresses. Many dogs with PKD can survive until 8 to 10 years of age, as long as appropriate treatment and monitoring are provided.

How is PKD prevented?

The only way to prevent PKD is to avoid breeding affected dogs. This can be challenging, because most dogs do not show any evidence of the disease until they are past prime breeding age. Given the increased risk of this condition in bull terriers, genetic testing is recommended to screen bull terriers prior to breeding. This test is relatively inexpensive and easy to perform. Talk to your veterinarian for more information.