Heterotopic hindgut duplication: a cloacal remnant associated with exstrophy of the bladder.

Lower hindgut duplications, although very rare, usually present as a cystic mass located posterior to the rectum and confined to the pelvis. Hindgut duplications are often associated with genitourinary or spinal anomalies. We describe a neonate with a previously unreported heterotopic colonic duplication presenting as an exophytic perineal mass associated with classic bladder exstrophy. The embryonic significance of these anomalies is discussed.