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Medullary Sponge Kidney

By Navin Jaipaul, MD, MHS, Associate Professor of Medicine, Loma Linda University School of Medicine; Chief, Nephrology, VA Loma Linda Healthcare System

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 nongenetic 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. Rarely, stones block the urinary tract.

A doctor may suspect medullary sponge kidney based on the symptoms and results of imaging tests done for other reasons. Imaging tests of the kidneys reveal calcium deposits if there are any. The diagnosis is usually made by computed tomography (CT), usually showing calcium deposits and widened (dilated) urine-containing tubules in 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 doctors recommend people take a thiazide diuretic to reduce the amount of calcium that is excreted in their urine. Surgery may be needed if the urinary tract becomes blocked. Infections are treated with antibiotics.