Medullary sponge kidney is an uncommon disorder in which the urine-containing tubules of the kidneys are dilated.

Medullary sponge kidney is usually caused by a non-genetic abnormality that occurs during development of the fetus. Much less often, the abnormality is hereditary. Medullary sponge kidney causes no symptoms most of the time, but a person with the disorder is prone to developing painful kidney stones, blood in the urine, and kidney infections. Calcium deposits in the kidneys occur in more than half of the people with the disorder. Calcium deposits may form kidney stones.

A doctor may suspect medullary sponge kidney based on the symptoms. X-rays of the kidneys reveal calcium deposits if there are any. The diagnosis is usually made by computed tomography (CT). Ultrasonography may help but may not detect tiny fluid-filled sacs (cysts) lying deep within the kidneys.

Most people do well without treatment. Treatment may be necessary if infection develops or if medullary sponge kidney causes calcium to deposit and repeatedly form stones. Treatment for calcium stones is high fluid intake (more than 2 quarts [2 liters] per day) and a diet that is low in sodium, normal in calcium, and low to normal in protein. Sometimes a thiazide diuretic or amiloride is recommended. Surgery may be needed if the urinary tract becomes obstructed. Infections are treated with antibiotics.

Last full review/revision December 2006 by Peter C. Brazy, MD