Approximately 1 in 4,000 infants are born with one kidney replaced by cysts, the so called Multicystic Dysplastic Kidney (MCDK). Diagnosis is usually made by prenatal ultrasound. The cysts can be small or very large and there is rarely any functional kidney tissue.

MCDK is not an inherited problem though it is sometimes confused with the 2 forms of Cystic Kidney Disease, which are inherited disorders. Instead, the kidney tissue simply does not form normally.

Follow-up

Fortunately, the other kidney is usually normal. After birth though it is important infants identified with MCDK on prenatal ultrasound have an ultrasound to confirm the MCDK and to assess the other kidney. Over the next 1-2 years most physicians recommend periodic ultrasound to make sure the normal kidney is growing appropriately.

In the past, infants with MCDK would routinely receive testing for vesicoureteral reflux. However, we do not do this testing unless the other kidney shows some abnormality on ultrasound or if the infant later develops a urinary tract infection. Also in the past, the MCDK would be routinely removed by surgery. That is rarely necessary as the cysts usually resorb and disappear over a few years and the risk of cancer or other medical problem related to the MCDK is extremely rare.