Bladder exstrophy is a rare malformation characterized by an infra-umbilical abdominal wall defect, incomplete closure of the bladder with mucosa continuous with the abdominal wall, epispadias, and alterations in the pelvic bones and muscles. Its incidence is estimated between 1/30 000–1/50 000 live births.1,2 From an embryological perspective, mesodermal ingrowth between the ectodermal and endodermal layers of the bilaminar cloacal membrane results in formation of the lower abdominal musculature and pelvic bones. Following mesenchymal ingrowth, downward growth of the rectal septum divides the cloaca into a bladder anteriorly and a rectum posteriorly. The genital tubercles migrate medially and fuse in the midline cephalad to the dorsal membrane before it perforates. The cloacal membrane is subject to premature rupture depending on the extent of the infraumbilical defect. The most recognized theory describes an abnormal lower overdevelopment of the cloacal membrane, which prevents the medial migration of the mesenchymal tissue, leading to disruption of the abdominal wall. The timing of the rupture of this cloacal defect determines the severity of the complex. Central perforations resulting in classic exstrophy have the highest incidence (60%), whereas exstrophy variants account for 30% and cloacal exstrophy for approximately 10%. These conditions are part of a spectrum, the bladder exstrophy-epispadias complex, with cloacal exstrophy on the severe and epispadias on the mild ends of the continuum. Bladder exstrophy remains the most common of these entities and is more common in boys.
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