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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
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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.
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Pathophysiology
and Genetics
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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.
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Clinical Features
and Differential Diagnosis
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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.
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GI bleeding is the most common presenting symptom associated with
a Meckel diverticulum, and ...