During the fourth week of human embryonic development, the lateral body wall folds of the embryo meet at the midline and fuse together to form the anterior body wall. However, in<unk>  and other anterior body wall defects, this fails to occur by either one or both of the lateral body wall folds not moving properly to meet with the other and fusing together. This incomplete fusion results in a defect that allows abdominal organs to protrude through the abdominal wall, and the intestines typically herniate through the rectus abdominis muscle, lying to the right of the umbilicus. The forces responsible for the movement of the lateral body wall folds are poorly understood, and a better understanding of these forces would help to explain why<unk>  occurs mostly to the right of the umbilicus, while other ventral body wall defects occur in the midline. At least six hypotheses have been proposed for the pathophysiology: # Failure of mesoderm to form in the body wall # Rupture of the amnion around the umbilical ring with subsequent herniation of bowel # Abnormal involution of the right umbilical vein leading to weakening of the body wall and gut herniation # Disruption of the right vitelline (yolk sac) artery with subsequent body wall damage and gut herniation # Abnormal folding of the body wall results in a ventral body wall defect through which the gut herniates # Failure to incorporate the yolk sac and related vitelline structures into the yolk sac The first hypothesis does not explain why the mesoderm defect would occur in such a specific small area. The second hypothesis does not explain the low percentage of associated abnormality compared with omphalocele. The third hypothesis was criticized due to no vascular supplement of anterior abdominal wall by umbilical vein. The fourth hypothesis was commonly accepted, but it was later shown that the right vitelline artery (right omphalomesenteric artery) did not supply the anterior abdominal wall in this area. More evidence is needed to support the fifth hypothesis.
Gastroschisis
Prune belly syndrome
Omphalocele
Rachischisis
Diaschisis
Cranioschisis
Intestinal atresia
Encephalocele