Pathophysiology
Clinical meaning
Meckel's diverticulum is the most common congenital anomaly of the gastrointestinal tract, affecting approximately 2% of the population. It is a small pouch (outpouching) of the intestinal wall located in the ileum (the last part of the small intestine), usually within about 2 feet (60 cm) of the ileocecal valve. This pouch is a remnant of the omphalomesenteric (vitelline) duct, which normally connects the developing intestine to the yolk sac during fetal development and usually disappears completely by the seventh week of gestation. The classic teaching for Meckel's diverticulum is the 'Rule of 2s': it occurs in 2% of the population, is about 2 inches long, is located within 2 feet of the ileocecal valve, is usually found before age 2, and may contain 2 types of ectopic (misplaced) tissue - gastric and pancreatic. When the diverticulum contains gastric tissue, it produces hydrochloric acid, which can erode the adjacent normal intestinal lining and cause painless rectal bleeding. This bleeding is the most common presentation in children and typically appears as brick-red or maroon-colored (currant jelly) stools.