Meckel's Diverticulum

Meckel's diverticulum is a congenital true diverticulum arising from the antimesenteric border of the distal ileum. It results from incomplete obliteration of the embryonic vitelline, or omphalomesenteric, duct and contains all layers of the bowel wall. That makes it different from acquired pseudodiverticula, which lack part of the muscular wall. Most people with a Meckel's diverticulum never develop symptoms. Complications occur in only a minority, but the consequences can be abrupt and serious: haemorrhage, obstruction, inflammation, perforation, or neoplasia. The mechanism of bleeding is especially important. A substantial minority of diverticula contain heterotopic tissue, most often gastric mucosa. Gastric parietal cells within the diverticulum secrete acid. The acid contacts the adjacent normal ileal mucosa, which lacks the same protective mechanisms as the stomach, producing an ulcer that can erode small arterioles and cause painless, sometimes brisk lower gastrointestinal bleeding. The ulcer is typically in the ileum beside the diverticulum, not inside the diverticulum itself. This anatomical detail later influences the choice and extent of resection. Pancreatic tissue is much less common than gastric heterotopia. The frequently quoted “rule of 2s”—2%...