Embryology and bony and pelvic floor anatomy in the bladder exstrophy-epispadias complex

The exstrophy-epispadias complex is a complex congenital anomaly that, although rare, remains the largest genitourinary birth defect that is surgically correctable. The primary defect in exstrophy is a derangement in midline developmental that presents with a spectrum of severity. In its mildest form, epispadias, the dorsal urethral unit is not fused and has failed to form into a tube. Next, patients with classic bladder exstrophy present with a bladder and urethra open and continuous with the abdominal wall; also associated is a failure of the abdominal muscles, pelvic ring, and pelvic floor musculature to fuse in the midline. Cloacal exstrophy, the most severe variant, includes exstrophied hindgut tube and a more severe degree of concomitant congenital derangements of musculoskeletal, genitourinary, gastrointestinal, and neurological systems. The embryology of the exstrophy-epispadias complex has been long studied, yet debate still exists over the specific origins of the anomaly. This article covers the embryologic theories of this congenital defect and the subsequent bony pelvic and pelvic floor muscular defects characteristic of exstrophy. Primarily, the anatomic focus will be on classic bladder exstrophy because it is the most common and well studied to date.