Bladder prolapse through a patent urachus presenting as an umbilical mass in the newborn: characteristic prenatal sonographic findings and the diagnostic benefit of postnatal cystography.

Bladder prolapse through a patent urachus is rare. We present a newborn with an unusual exophytic, erythematous umbilical mass. Voiding cystography readily demonstrated continuity of the bladder dome with the umbilical mass, confirming bladder prolapse through a patent urachus. The diagnosis of bladder prolapse was rapidly made in a second newborn with similar imaging and clinical findings and confirmed by cystography. We discuss the embryology of this condition including the association with a vesico-allantoic cyst in utero. Pre- and postnatal images are presented. The use of cystography in diagnosis is emphasized.