Congenital malformations - Edocr

Chapter 34
Duodenal Atresia
PRAVEEN KUMAR
INTRODUCTION
Duodenal atresia, complete occlusion of the
duodenal lumen, is a frequent cause of congenital
intestinal obstruction. Duodenal atresia
can be classified into the following three types
as described by Gray and Skandalakis: (1) type I
defects are most common and represent a mucosal
web with normal muscular wall; (2) type II
defects represent a short fibrous cord connecting
the two atretic ends of the duodenum; and
(3) type III defects are least common and represent
complete separation of atretic ends with
no connecting tissue.
EPIDEMIOLOGY/ETIOLOGY
Duodenal atresia is reported to occur in 1 per
5000–10,000 live births. Nearly 50% of all intestinal
atresias occur in the duodenum. 2 Polyhydramnios
and prematurity are present in
nearly half of all cases. Initial studies had reported
a male preponderance which has not
been confirmed by more recent studies. 1,3 Large
epidemiological studies have not reported any
significant changes in its incidence over the last
several decades, but observed higher incidence
with multiple births. 2,4,5
EMBRYOLOGY
The development of the duodenum begins in the
early fourth week from the caudal part of the
foregut, proximal part of the midgut, and the surrounding
splanchnic mesenchyme. The foregut
and midgut junction is just distal to the origin of
common bile duct and is a frequent site for atresia.
During the fifth and sixth weeks of gestation,
there is exuberant growth of the intestinal epithelial
lining which completely blocks the small
lumen of the developing gut. Subsequent degeneration
of these cells and recanalization of the
lumen is complete by the end of the eighth to
tenth week of gestation and an interruption of this
process can lead to loss of lumen in that area. Excessive
epithelial formation versus failure of recanalization
as a cause of atresia remains an issue
of debate. Another mechanism proposed is vascular
infarction followed by atrophy of the affected
segment in a small number of cases. Observations
of duodenal stenosis in sonic hedgehog mutant
mice have suggested that mutations in signaling
pathways may play a role in the development of
duodenal atresia. 6 Recently, fibroblast growth
factor 10 is reported to serve as a regulator in
normal duodenal growth and development and
its deletion has been implicated in the pathogenesis
of duodenal atresia. 7
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