Challenging the embryogenesis of cloacal exstrophy.

As presently understood, cloacal exstrophy results from a migration failure of the lateral mesodermal folds of the infraumbilical anterior abdominal wall, and rupture of the resulting enlarged, persistent cloacal membrane before the eighth week of gestation. The authors present ultrasonographic evidence that disputes this embryological theory. Routine ultrasonography of a twin gestation at 18 weeks showed that one twin had a dilated cloacal abnormality, bilateral hydronephrosis, and oligohydramnios. Repeat ultrasonography at 24 weeks demonstrated rupture of the cloacal anomaly, with resolution of both the hydronephrosis and oligohydramnios. This twin was born with classic cloacal exstrophy. This striking ultrasound evidence of an intact cloacal membrane at 18 weeks, which ruptured before 24 weeks, relieving the urinary tract outlet obstruction, forces us to rethink how this surgically correctable anomaly develops.