i) Meckel's Diverticulum. The yolk stalk (vitelline duct) normally regresses completely during the 6th week of the development. However, in about 2% of people its proximal part persists as a diverticulum called Meckel's diverticu-lum or ileal diverticulum. It is usually observed as a finger-like pouch about 5 cm (2 inches) long that arises form the antimesenteric border of the ileum, 50 to 60 cm (about 2 feet) from the ileoce-cal valve. This anomaly is more common in males than females. The Meckel's diverticulum carries great clinical significance because it sometimes becomes inflamed and causes symptoms mimicking appendicitis. As mentioned earlier, the wall of the Meckel's diverticulum may contain het-erotropic gastric mucosa or pancreatic tissue. The acid produced by the gastric mucosa may cause ulceration, bleeding, or even perforation of the diverticulum. Treatment consists of surgical removal of the diverticulum.
ii) Vitelline cyst. This is a rare type of anomaly resulting from the failure of disappearance of the yolk stalk. In this malformation the proximal and distal parts of the yolk stalk transform into fibrous cords, while the middle portion forms a big cyst called vitelline cyst (also called enterocyst or entero-cystoma}. Because the fibrous cords
traverse the peritoneal cavity, intestinal loops may become twisted around these fibrous cords, producing a volvulus of the intestine.
Hi) Umbilico-ileal Fistula. In this rare anomaly the yolk stalk persists and remains patent over its entire length, forming fistulous communication between the umbilicus and small intestine. Fecal matter escapes from the fistula. The condition can be corrected by surgery.