DUODENAL MALFORMATIONS

Duodenal Malformations Can be intrinsic (Atresia, Stenosis, Webs) or extrinsic (Annular pancreas, Ladd's bands). Occur distal or proximal to the ampulla of Vater. Most commonly distal to ampulla and therefore bilious vomiting is present. (Note: Bilious vomiting is surgical until proven otherwise in a baby).
"Windsock" webs have clinical importance because of their tendency to be confused with distal
duodenal obstruction and because of the frequent occurrence of an anomalous biliary duct entering along their medial margin.

Embryology: The first major event in the differentiation of the duodenum, hepatobiliary tree, and
pancreas occurs at about the third week in gestation, when the biliary and pancreatic buds form at the junction of the foregut and the midgut. The duodenum at this time is a solid cord of epithelium, which undergoes vacuolization followed by recanalization and restitution of the intestinal lumen over 3-4 weeks of normal development. Failure of recanalization of the second part of the duodenum results in congenital obstruction of the lumen, often in conjunction with developmental malformation of the pancreatic anlagen and the terminal part of the biliary tree. In support of this concept is the high incidence of annular pancreas observed, believed to represent a persistence of the ventral pancreatic anlage in association with intrinsic duodenal obstruction.

The diagnostic characteristics are: bilious vomiting, history of polyhydramnios in mother, KUB with
classic "Double-bubble" appearance, a microcolon in barium enema study or malrotation.

Treatment consist in: (1) duodeno-duodenostomy bypass for atresias, annular pancreas, and some
stenosis. (2) duodenoplasty for webs, and stenosis, and (3) lysis of Ladd's bands and Ladd's procedure for malrotation.

Associated anomalies are: Down's syndrome (20-30%), VACTERL syndrome, CNS anomalies and
cardiac anomalies.