A cloaca is a common passageway for feces, urine and reproduction. During human embryogenesis (development), there is for a time a cloaca. The far end of a structure called the hindgut is the cloaca before it divides to form a rectum, a bladder, and genitalia.
Exstrophy refers to the eversion of a hollow organ at birth (from the Greek ex, out, + strophe, a turning). In exstrophy of the cloaca, an area of the intestine is interposed between two separate areas of the bladder. Variations on this theme occur in cloacal exstrophy, resulting in grave anatomic disarray.
Cloacal exstrophy can affect boys or girls. However, in at least one respect the condition is even more devastating for boys than girls. Boys with cloacal exstrophy have cryptorchidism (failure of descent of the testes into the scrotum) and very severe epispadias (with the urine opening above the phallus). This is so severe that it usually makes adequate reconstruction (of the male genitalia) difficult, if not impossible. Gender reassignment has therefore sometimes been attempted, making boys with cloacal exstrophy into apparent girls. In psychological and emotional terms, the results have been controversial.