label: Vesicoallantoic abdominal wall defect
label_lc: vesicoallantoic abdominal wall defect
description: "An abdominal wall defected related to a developmental anomaly of the allantois, which is an embryonic structure that develops as a diverticulum off the yolk sac at about 16 days post fertilization. During further development, the allantois becomes incorporated into the body of the embryo, connecting the ventral aspect of the urogenital sinus (which will develop into the upper pole of the urinary bladder) to the external portion of the umbilicus. Upon further development, the lumen of the allantois becomes obliterated and forms a thick fibrous cord called the urachus, which connects the apex of the bladder to the umbilicus. In adults, the urachus is known as the median umbilical ligament. Failure of the allantoic cavity to obliterate can result of one of four conditions: 1) congenital patent urachus (a completely open connection between bladder and umbilicus); 2) vesicourachal diverticulum (a diverticulum off the bladder but not communicating with the umbilicus); umbilical cyst and sinus (not communicating with the bladder); and 4) alternating urachal sinus. An abdominal wall defect can be associated with a urachal cyst."