++
An “unusual” diverticulum of the small intestine was first described by Fabricius Hildanus in 1598, but Johannes Meckel wrote the first definitive description of the Meckel diverticulum in 1809. The vitelline (or omphalomesenteric) duct normally involutes by the ninth week of gestation, but persistence of all or portions of this duct can result in a spectrum of abnormalities of the omphalomesenteric duct, such as a fistula, cyst, umbilical sinus, or mesodiverticular bands (Fig. 397-1).
++
The omphalomesenteric duct is an embryologic communication between the yolk sac and the primitive midgut of the developing embryo. This connection includes vessels that provide nutrition to the embryo until the placenta develops. Intestinal lengthening occurs during the 4th to 8th weeks of gestation as the bowel herniates into the umbilical cord and the omphalomesenteric duct closes its lumen to form a band. This band is typically absorbed by the 10th week of gestation when the bowel returns to the abdominal cavity. Incompletely absorbed omphalomesenteric duct remnants can persist as a variety of anomalies.
++
Meckel diverticulum is the most common congenital abnormality of the small intestine, occurring in 2% of the population. In general, Meckel diverticulum follows the rule of twos: affecting 2% of the population; found 2 feet from the ileocecal valve; 2 types of ectopic tissue may be found within the diverticulum (gastric and pancreatic tissue); and 2% develop symptoms. The lifetime risk of complications from Meckel diverticulum has been estimated to be between 4% and 6%. Since many of these are asymptomatic, Meckel diverticula are often identified incidentally during operations for other pathology. Treatment is often dictated by presenting symptoms, the age of the patient, and the anatomy of the diverticulum. While most Meckel diverticula are sporadic, there is an association with Hirschsprung disease, Down syndrome, esophageal atresia, duodenal atresia, malrotation, and congenital cardiac abnormalities. Other omphalomesenteric duct abnormalities are much less common.
++
A Meckel diverticulum is a true diverticulum, as it has all the layers of the gut wall. It is typically found on the antimesenteric border of the ileum, with a blood supply from a terminal branch of the superior mesenteric artery (vitelline artery). More than half of diverticula may have ectopic gastric and/or pancreatic tissue contained within it, which can lead to symptoms.
+++
CLINICAL FEATURES AND DIFFERENTIAL DIAGNOSIS
++
The most common presentations of a Meckel diverticulum include painless lower gastrointestinal (GI) hemorrhage, inflammation with or without perforation, and bowel obstruction from volvulus, intussusception, or internal hernia (Fig. 397-1). Such presentations often mimic other pathology requiring emergent surgery, and therefore, diagnosis of a Meckel diverticulum is often made only in the operating room.
++