A Meckel's diverticulum is a true congenital diverticulum. It is a vestigial remnant of the omphalomesenteric duct , and is the most frequent malformation of the gastrointestinal tract. It is present in approximately 2% of the population, with an equal distribution between males and females, although males more frequently experience symptoms. It is named after Johann Friedrich Meckel , who first described this type of diverticulum in 1809.

Approximately 98% of people afflicted with Meckel's diverticulum are asymptomatic. If symptoms do occur, they typically appear before the age of two.

Meckel's diverticulum is located in the distal ileum, usually within about 60-100 cm of the ileocecal valve . It is typically 3-5 cm long, runs antimesenterically and has its own blood supply. A memory aid is "2 percent (of the population) - 2 feet (from the ileocecal valve) - 2 inches (in length)".

The most common presenting symptom is painless rectal bleeding , followed by intestinal obstruction , volvulus and intussusception. Occasionally, Meckel's diverticulitis may present with all the features of acute appendicitis .

A technetium-99m (99mTc ) pertechnetate scan is the investigation of choice to diagnose Meckel's diverticula. This scan detects gastric mucosa ; since approximately 50% of Meckel's diverticula have ectopic gastric (stomach) cells contained within them, this is displayed as a spot on the scan distant from the stomach itself. Patients with these misplaced gastric cells may experience peptic ulcers as a consequence. Other tests such as colonoscopy and screenings for bleeding disorders should be performed, and angiography can assist in determining the location and severity of bleeding.

Treatment is surgical, consisting of a resection of the affected portion of the bowel.