Pathology
Congenital obstruction of the duodenum was first reported by Calder
in 1733. Duodenal obstruction is the result of atresia, stenosis,
and duodenal web, annular pancreas, or peritoneal bands secondary to
incomplete intestinal rotation. Intrinsic anomalies of the duodenum
occur in several forms. There can be atresia with continuity of the
bowel wall, atresia with a fibrous cord joining the segments,
atresia with complete loss of continuity of the wall and of the
blood supply, and all but complete diaphragm with a small
fenestration, or a membranous ring within the duodenum which
peristalsis from above forces into the development of a "wind sock".
The dilating effect of the wind sock may produce the appearance of
obstruction distal to the actual annulus of the wind sock.
The pathogenesis of duodenal obstruction remains somewhat
unclear. Early in fetal life the duodenum undergoes a proliferation
which causes complete obliteration of the lumen in the 5th to 6th
week of fetal life. This is followed by recanalization in the 8th to
10th week of fetal development. The lack of complete recanalization
produces an atresia or stenosis. There is evidence that there is
some relationship between congenital intestinal atresia in the fetus
and hydramnios in the mother. Vascular catastrophes and early
intrauterine intussusception have been implicated by other writers
as possible factors in pathogenesis. About 25% of patients with
duodenal obstruction also have Down's syndrome.
The clinical presentation depends on the degree of atresia or
stenosis that is present. The majority of obstructions are distal to
the ampulla of Vater. Bilious vomiting without abdominal distention
is the cardinal sign in the patient with a duodenal obstruction.
High grade obstructions will obviously present within the first few
days of life. Less severe obstructions may allow a child to go
several months or even years prior to diagnosis. Weight loss,
dehydration, and hypochloremic metabolic alkalosis are common.
Abdominal x- rays typically show the double bubble picture with air
trapped in the first portion of the duodenum and stomach.
Duodenal obstruction is commonly associated with Down's syndrome,
esophageal atresia, and tracheoesophageal fistula. Other associated
anomalies include lymphangiomatous cysts of the mesentery, vertebral
anomalies, club feet, congenital heart disease, mental retardation,
and Meckel's diverticulum.The differential diagnosis would include
pyloric stenosis, other intestinal atresia, midgut volvulus, and
sepsis
Duodenal atresia is
thought to be caused by delayed vacuolization of the embryonic
intestinal lumen, but may also be caused by vascular compromise in
utero. Patients usually present with vomiting in the first few hours
of life. Bile is frequently seen in the vomitus since the
obstruction is usually at or below the Ampulla of Vater. In a few
cases, the KUB will show gas distal to the area of obstruction. This
can be explained by an associated anomaly of the hepaticopancreatic
ducts due to persistence of the fetal double orifice in the ducts
which allows for one limb of the duct to open into the duodenum
above the point of atresia and one below. Also, it is important to
note that 1/3 of cases of duodenal atresia occur in patients with
Trisomy 21. |
