Review Question - QID 106469

Annular pancreas (pancreas surrounding descending part of duodenum) can cause duodenal obstruction resulting in bilious (green to bright yellow) or non-bilious vomiting in the newborn. It is the result of abnormal migration of ventral pancreatic bud.

Annular pancreas is a rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous with the head of the pancreas. This portion of the pancreas can constrict the duodenum and block or impair the flow of food to the rest of the intestines. Obstruction can be partial, intermittent, or severe. Age of onset and degree of symptoms depend on the severity of duodenal constriction. It usually presents with early bilious vomiting, low birth weight, and can be associated with polyhydramnios. In neonates, annular pancreas is typically diagnosed when a plain abdominal radiograph or ultrasound showing the classic "double bubble" sign suggestive of duodenal obstruction. While this is not specific for annular pancreas, no further testing is usually required because all patients in this age group with complete or partial duodenal obstruction require surgical correction and definitive diagnosis will be made at that time.

Incorrect Answers:
Answer 2: Complete failure of proximal duodenum to recanalize would have a similar presentation as the one described in the vignette but the onset would be within hours of birth, and the vomiting would be NON-bilious because the obstruction would be proximal to the ampulla of vater.
Answer 3: Error in neural crest cell migration would produce Hirschsprung's disease, which is characterized by failure to pass stool within the first 48 hours and megacolon.
Answer 4: Abnormal hypertrophy of the pylorus would produce pyloric stenosis. This would typically produce projectile, NON-bilious vomiting as opposed to the bilious vomiting described in the vignette.
Answer 5: Failure of lateral body folds to move ventrally and fuse in the midline would produce gastroschisis. This abnormality would be evident immediately after birth and would be characterized by a defect in the anterior abdominal wall in which the abdominal contents freely protrude.