Speaking of Kidneys

By Peter Galvin, MD

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic, or inherited, cause of kidney failure. An individual has a 50% chance of inheriting the disease when one parent has it. In about 15% of cases, however, ADPKD arises from a genetic variant, or mutation, which is not inherited from a parent. It affects between 1 in 1000 and 1 in 2500 people worldwide and involves progressive growth of fluid-filled cysts in the kidneys. People with ADPKD may also have cysts in their liver or pancreas, abdominal hernias, and cardiac valve abnormalities. Between 9% and 12% of patients with ADPKD have brain blood vessel abnormalities (aneurysms) which, on rare occasions may burst, resulting in permanent neurologic damage (i.e., stroke) or death.

In the early stages of the disease, many people with ADPKD have no symptoms, although they may have high blood pressure. As the kidney cysts increase in size, patients may develop abdominal pain or pressure, blood in the urine, kidney infections, and kidney stones. Over time, more than half of those with ADPKD develop kidney failure and require treatment such as dialysis or kidney transplant. The onset of kidney failure is usually after age 50 years but can occur earlier. The recommended imaging test to diagnose ADPKD is ultrasound, which reveals cysts in the kidneys. Other tests such as MRI or CT may be performed, but ultrasound alone is usually sufficient to make the diagnosis, along with a blood test for kidney function.  The presence of cysts will confirm the diagnosis for those with a family history of ADPKD. If the diagnosis is still uncertain after imaging and blood tests, genetic testing can be done to confirm the diagnosis.

In ADPKD, certain genetic variants are associated with milder and more severe disease, however people with the same variant may progress to kidney failure at different rates. Kidney volume (size) can be helpful at predicting the onset of kidney failure because larger kidney size is associated with greater loss of kidney function. There is no cure for ADPKD, however treatments are available to improve outcomes. Medications to lower blood pressure can slow the progression to kidney failure. Those with ADPKD should maintain an optimal weight, engage in regular physical activity, have high water intake, limit salt to five grams per day, avoid smoking, and limit the use of non-steroidal anti-inflammatory drugs such as ibuprofen. A medication called tolvaptan can be prescribed by kidney specialists to those at higher risk of kidney failure.

Asymptomatic children of those with ADPKD should be closely monitored for high blood pressure but do not require screening before adulthood. Prior to being tested for ADPKD, adults with a family history of it should be counseled about the benefits of screening (timely initiation of treatment if ADPKD is diagnosed or reassurance if it is ruled out) and the risks of screening (potential problems with health insurance coverage and the psychological aspects of being diagnosed with a genetic disease). Finally, there is also an autosomal recessive form of PKD, but it is usually diagnosed in the very first months of life, often while the child is still in the womb.

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