Chapter 402

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 omphalo-mesenteric) connects the yolk sac to the primitive gut. It normally involutes by the ninth week of gestation, but persistence of all or portions of this duct can result in a Meckel diverticulum or other abnormalities of the omphalomesenteric duct, such as omphalomesenteric fistula, omphalomesenteric cyst, umbilical sinus, or mesodiverticular bands.1

### Epidemiology

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: affects 2% of the population; most commonly found 2 feet from the ileocecal valve; 2 types of ectopic tissue are found within the diverticulum (gastric and pancreatic tissue); and 2% develop symptoms. In fact, the life-time risk of complications from Meckel diverticulum has been estimated to be between 4% and 6%.2 Given the low number of symptomatic diverticula, many Meckel diverticula are identified incidentally during operations for other pathology. While most Meckel diverticula are sporadic, there is an association with Hirschsprung disease, Down syndrome, esophageal atresia, duodenal atresia, malrotation, and congenital cardiac abnormalities.3 Other omphalomesenteric duct abnormalities are much less common.

### Pathophysiology and Genetics

Normal gut development depends on the interactions among the layers of endoderm (epithelial lining), mesoderm (smooth muscle formation) and ectoderm (enteric nervous system). Histologically, a Meckel diverticulum is a true diverticulum, consisting of all four intestinal layers. The blood supply is a vestige of the primitive vitelline artery and may be prominent in patients with bleeding presentations (see Fig. 402-1). Murine studies noted formation of buds at the region of the vitelline duct in approximately 3% of 13.5-day embryos. The tissue from these buds was able to express albumin; the remainder of the surrounding tissue did not, suggesting an escape from the inhibitory effects of the mesoderm.4 Further studies are necessary to delineate the complex pathway leading to the development of a Meckel diverticulum.

###### Figure 402-1.

Omphalomesenteric remnants. A: Meckel diverticulum with diverticulitis. B: Meckel diverticulum with ulceration and hemorrhage. C, D: Bowel obstruction from volvulus around attachment to the abdominal wall. E: Patent omphalomesenteric duct. F: Omphalomesenteric sinus and cyst.

### Clinical Features and Differential Diagnosis

The most common presentations of symptomatic a Meckel diverticulum include painless lower gastrointestinal (GI) bleeding, inflammation with or without perforation, or bowel obstruction from volvulus, intussusception, or internal hernia (see Fig. 402-1). Such presentations often mimic other pathology requiring emergent surgery and therefore diagnosis of a Meckel diverticulum is often made only in the operating room.

GI bleeding is the most common presenting symptom associated with a Meckel diverticulum, ...

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