Description

The exstrophy–epispadias complex is a rare spectrum of multisystem birth defects involving the genitourinary and gastrointestinal tracts, musculoskeletal system, pelvic floor, and bony pelvis. It is composed of epispadias, bladder exstrophy, and cloacal exstrophy. The latter two conditions present with an open bladder through the anterior abdominal wall.

• The least common variant of the complex, complete epispadias, presents with a closed bladder and a dorsally displaced urethral meatus. The urethra is replaced by a broad mucosal strip on the dorsum, and urinary incontinence is related to the location of the meatus.
• Cloacal exstrophy is the most severe variant, presenting with a large omphalocele, imperforate anus, shortened colon, bladder halves with cecum interposed between, associated cord defects, and multiple upper urinary tract and limb anomalies. All three forms are associated with a pubic diastasis.

Epidemiology

• Bladder exstrophy
  • Male-to-female ratio is between 2:1 and 4:1.
  • Between 1:10,000 and 1:50,000 live births
  • Risk in offspring of individuals with bladder exstrophy and epispadias is 1:70 (500-fold greater than general population).
  • Risk of recurrence in family is approximately 1:100.
• Epispadias
  • Risk of male epispadias: 1:117,000 live births
  • Risk of female epispadias: 1:484,000 live births
• Cloacal exstrophy
  • Male-to-female ratio is between 1:1 and 2:1.
  • Cloacal exstrophy is exceedingly rare, with an incidence between 1:200,000 and 1:400,000 births (decreasing incidence with prenatal diagnosis and termination).

Risk Factors

Bladder exstrophy: Only known association is related to offspring of in vitro fertilization pregnancies.

Pathophysiology

Embryology

• Normal development
  • By week 2 of gestation, the cloacal membrane is located at the caudal end of the infraumbilical abdominal wall.
  • At week 4 of gestation, mesenchyme from the primitive streak migrates between the layers of the cloacal membrane to reinforce the abdominal wall while the cloacal membrane regresses.
• Bladder exstrophy
  • Unclear pathogenesis, but there is an error in embryogenesis
  • The cloacal membrane may overdevelop and prevent mesenchymal migration, which inhibits formation of normal lower abdominal wall.
  • Without reinforcement, the cloacal membrane ruptures. The timing of this rupture determines the variant of the exstrophy–epispadias complex. In bladder exstrophy, rupture of the membrane occurs after the urorectal septum has descended, dividing the genitourinary and gastrointestinal tracts.
• Cloacal exstrophy
  • Abnormally large cloacal membrane ruptures prior to division of the cloaca by the urorectal septum.