Duodenal obstruction

Congenital duodenal obstruction may be due to intrinsic lesions, extrinsic lesions, or both. Intrinsic duodenal obstruction may be caused by duodenal atresia, stenosis, diaphragm, a perforated diaphragm or a ‘wind-sock’ web. The wind-sock web is a duodenal membrane which is ballooned distally as a result of peristalsis from above. Extrinsic duodenal obstruction may be caused by the annular pancreas, malrotation or preduodenal portal vein. Although the annular pancreas forms a constricting ring around the second part of the duodenum, it is not believed to be the cause of duodenal obstruction and there is usually an associated atresia or stenosis in patients with an annular pancreas. Atresias have traditionally been classified by the method described by Gray and Skandalakis, who identified three types of lesions. Type I defects, the most common, are represented by a mucosal web with a normal muscular wall, type II by a short fibrous cord connecting the two atretic ends of the duodenum, and in type III by a complete separation of the atretic ends. The recently reported prevalence of type I is about 65% and of types II and III 18% each; duodenal stenosis is approximately half as prevalent as atresia 9.