Background
The exstrophy-epispadias complex comprises a spectrum of congenital abnormalities that includes classic bladder exstrophy, epispadias, cloacal exstrophy, and several variants. Each of these anomalies is thought to result from the same embryologic defect.
Separation of the primitive cloaca into the urogenital sinus and hindgut occurs during the first trimester at approximately the same time as maturation of the anterior abdominal wall. Failure of mesenchyme to migrate between the ectodermal and endodermal layers of the lower abdominal wall leads to instability of the cloacal membrane.
Premature rupture of the membrane before its caudal translocation leads to this complex of infraumbilical anomalies. Rupture of the cloacal membrane after complete separation of the genitourinary and gastrointestinal (GI) tracts results in classic bladder exstrophy. However, rupture prior to descent of the urorectal septum allows externalization of the lower urinary tract and the distal GI tract (cloacal exstrophy).
Cloacal exstrophy must be distinguished from the condition of persistent cloaca or cloacal malformation. The latter terms refer to the most extreme form of anorectal malformation in female infants. This complex anomaly involves incomplete separation of the urinary tract, genital tract, and hindgut. No abdominal wall defect is present in persistent cloaca.
Epispadias is a variant that displays normal bladder formation but incomplete urethral tubularization from the bladder neck down.