Antenatal diagnosis of renal duplication by ultrasonography: report on four cases at a referral center.

Duplication of the renal collecting system is the commonest major congenital malformation of the urinary tract, with an incidence of 1% among live births. Antenatal diagnosing of renal duplication and an associated ureterocele is infrequent. We report four cases of prenatally diagnosed unilateral duplication of the renal collecting system. In two of them, the renal duplication was associated with an ectopic ureterocele.