Exstrophy of the cloacal membrane. A pathologic study of four cases.

Exstrophy of the cloaca is a rare congenital anomaly. The authors add the pathologic findings of four distinct cases reported in this article to those reported in the literature. In all cases, common anomalies were recognized. In addition, there were rare anomalies, such as single umbilical artery, vestige of the left superior vena cava, common mesenterium, calcification of the cerebellum, incomplete segmentation of the left lung, abnormal shape of the liver, and knock-knee. The embryology of this complex anomaly is difficult. It is considered that this anomalous condition results from breakdown and mesodermal invasion of the cloacal membrane.