mechanism of the diverticulum that attempts to remove irritating factors A passive process such as the transit of food Umbilical anomalies Anomalies between the diverticulum and umbilicus may include the presence of fibrous cord, cyst, fistula, or sinus, leading to: Infection or excoriation of periumbilical skin, resulting in a discharging sinus Recurrent infection and healing of sinus Abscess formation in the abdominal wall Fibrous cord increases the risk of volvulus formation and internal herniation Neoplasm Tumors in Meckel's diverticulum may cause bleeding, acute abdominal pain, gastrointestinal obstruction, perforation or intussusception. Benign tumors: Leiomyoma Lipoma Vascular and neuromuscular hamartoma Malignant tumors: Carcinoids: most common, 44% Mesenchymal tumors: Leiomyosarcoma, peripheral nerve sheath and gastrointestinal stromal tumors, 35% Adenocarcinoma, 16% Desmoplastic small round cell tumor Other complications A diverticulum inside a Meckel's diverticulum (daughter diverticula) Stones and phytobezoar (a bezoar of vegetable fibers) in Meckel's diverticulum Vesicodiverticular fistula Pathophysiology The omphalomesenteric duct (omphaloenteric duct, vitelline duct, or yolk stalk) normally connects the embryonic midgut to the yolk sac ventrally, providing nutrients to the midgut during embryonic development. The vitelline duct narrows progressively and disappears between the 5th and 8th weeks of gestation. In Meckel's diverticulum, the proximal part of vitelline duct fails to regress and involute, which remains as a remnant of variable length and location. The solitary diverticulum lies on the antimesenteric border of the ileum (opposite to the mesenteric attachment) and extends into the umbilical cord of the embryo. The left and right vitelline arteries originate from the primitive dorsal aorta, and travel with the vitelline duct. The right becomes the superior mesenteric artery that supplies a terminal branch to the diverticulum, while the left involutes. Having its own blood supply, Meckel's diverticulum is susceptible to obstruction or infection. Meckel's diverticulum is located in the distal ileum, usually within 60–100 cm (2 feet) of the ileocecal valve. This blind segment or small pouch is about 3–6 cm (2 inch) long and may have a greater lumen diameter than that of the ileum. It runs antimesenterically and has its own blood supply. It is a remnant of the connection from the yolk sac to the small intestine present during embryonic development. It is a true diverticulum, consisting of all 3 layers of the bowel wall which are mucosa, submucosa and muscularis propria. As the vitelline duct is made up of pluripotent cell lining, Meckel's diverticulum may harbor abnormal tissues, containing embryonic remnants