A sac that may form in the small intestine, present at birth.

a congenital diverticulum in the ileum resulting from incomplete closure of the yolk sac

An outpouching from the small intestine, due to failure of obliteration of the yolk stalk (which normally disappears during embryonic life). About 2% of people have a Meckel's diverticulum. It is usually located about 2 feet (60 cm) above the junction of the small intestine with the colon (the large intestine). A Meckel's diverticulum can become inflamed, ulcerate, bleed, perforate or cause obstruction of the small bowel. If it is inflamed or perforated, it is usually removed by surgery. See the entire definition of Meckel's diverticulum