What is polycystic kidney disease?
Polycystic kidney disease (PKD) is a hereditary kidney disease that is common in cats, but uncommon in dogs.
Affected dogs begin to develop multiple small cysts within both kidneys early in life. As the dog ages, these cysts gradually begin to increase in both size and number. As they multiple, the cysts replace normal, functioning kidney tissue. This leads to a decrease in the amount of kidney tissue that is available to remove waste products from the bloodstream. Over time, affected dogs begin to develop signs of chronic kidney disease.
What causes polycystic kidney disease?
Polycystic kidney disease is an inherited condition. It is inherited in an autosomal dominant manner, meaning that dogs who receive a defective copy of the gene from either one of their parents may show signs of polycystic kidney disease.
Polycystic kidney disease is most commonly diagnosed in Bull Terriers. Other predisposed breeds include Cairn Terriers and West Highlight White Terriers.
What are the signs of polycystic kidney disease?
In young dogs, polycystic kidney disease is typically (although not always) asymptomatic. As dogs age, functional kidney is gradually displaced by cysts and kidney function decreases. The clinical signs of polycystic kidney disease are often first observed in mature, middle-aged dogs.
Signs of kidney disease are variable. You may notice that your dog is drinking or urinating more than usual in an effort to help the kidneys to continue filter out waste products. Your dog may experience a decreased appetite or weight loss as an early sign of kidney disease. In later stages, nausea, vomiting, or diarrhea may occur, as a result of waste product buildup within the blood stream.
How will my veterinarian diagnose polycystic kidney disease?
Your veterinarian will begin by performing a physical exam. In some cases, your veterinarian may be able to detect enlarged or irregular kidneys on abdominal palpation. More frequently, however, the only signs on physical exam are nonspecific signs such as weight loss.
After a thorough physical exam, your veterinarian will likely perform blood tests. These tests typically include a complete blood cell count (CBC) and serum biochemistry. Your dog’s CBC may show evidence of anemia, which can occur when diseased kidneys fail to adequately stimulate red blood cell production. Your dog’s serum biochemistry will likely show elevations in two indicators of kidney function: blood urea nitrogen (BUN) and creatinine.
Your veterinarian will also perform a urinalysis. This tests involves analyzing the chemical composition of your dog’s urine, as well as examining the urine under a microscope. A urinalysis can indicate how well your dog’s kidneys are functioning, as well as assessing for the presence of a urinary tract infection.
"Imaging is often required to detect polycystic kidney disease."
Imaging is often required to detect polycystic kidney disease. Radiographs (X-rays) can sometimes show visibly enlarged and irregular kidneys, but may not be sensitive enough to diagnose early polycystic kidney disease. Ultrasound is typically recommended as a more sensitive test. It provides a much more detailed view of the kidneys, allowing small, individual cysts to be detected, even in young puppies.
Additional diagnostic tests that may be used to diagnose polycystic kidney disease include genetic testing, histopathology (examining kidney tissue under a microscope), and computed tomography (CT scan).
How is polycystic kidney disease treated?
There is no specific treatment for polycystic kidney disease. Dogs with polycystic kidney disease are treated the same as dogs with any other form of chronic kidney disease. Treatments may include prescription diet, fluid supplementation, and medications to manage the effects of chronic kidney disease.
Dogs vary significantly in how rapidly cyst development and signs of renal failure will progress. Many dogs with polycystic kidney disease can survive to 8-10 years of age, as long as appropriate treatment and monitoring are provided.
How is polycystic kidney disease prevented?
The only way to prevent polycystic kidney disease 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 is easy to perform. Talk to your veterinarian for more information.