Exstrophy of the bladder and associated anomalies.

Bladder exstrophy is a rare malformation of the urogenital tract. Its incidence is about one per 25,000-40,000 births, with a two to one ratio of males over females. No hereditary factors have been established, and it has been stated in the literature repeatedly that this defect does not occur with an increased frequency in the same family. However, Higgins reports bladder exstrophy in twins on two occasions, and twice in brothers and sisters.