Covered cloacal exstrophy: another variation on the theme.

Two cases showing many of the visceral features of exstrophy of the cloaca are described. In addition, there were the typical pelvic skeletal deformity and lumbosacral spina bifida but the abdominal wall was intact, although thin and weak. The embryogenesis is discussed. It is considered that the condition resulted from the breakdown of an infra-umbilical membrane at the 5 mm. stage. Later, mesodermal infiltration led to secondary closure of the membrane but visceral development was halted.