Meckel's Diverticulum

Meckel's diverticulum is a congenital true diverticulum of the distal ileum. It develops when the omphalomesenteric, or vitelline, duct—which connects the fetal intestine with the yolk sac—fails to disappear completely. Because it is a true diverticulum, its wall contains all layers of the bowel. It projects from the antimesenteric border, the side of the ileum opposite the mesenteric attachment. Its location is usually within about 40–60 cm, or 2 feet, of the ileocecal valve. The familiar “rule of 2s” is a memory aid, not a diagnostic rule: roughly 2% of people have one, it is often about 2 inches long, symptomatic cases commonly present before age 2, symptomatic males outnumber females by about 2:1, and gastric and pancreatic tissue are the two most common forms of heterotopic tissue. Most diverticula never cause symptoms. The clinical problem begins when the pouch contains ectopic gastric mucosa. That tissue secretes acid, but the neighboring ileum does not have the same protective lining as the stomach. Acid therefore produces an ulcer in adjacent ileal mucosa—the diverticulum is the source of the acid, but the...