Meckel diverticulum

**Definition:** A congenital abnormality characterised by the outpouching or sac formation in the ileum. It is a remnant of the embryonic yolk sac in which the vitelline duc failed to close. During early gestation, the omphalomesenteric or vitelline duct connects the fetal yolk sac to the primitive gut. By 7-8 weeks of gestation, this duct is normally completely obliterated. A Meckel diverticulum results when this structure fails to resorb completely.