An infant has persistent non-bilious vomiting with an upper gastrointestinal series showing complete duodenal obstruction at the level of the second part, with pancreatic tissue encircling the duodenum. This annular pancreas results from abnormal development of which structure?

• A Dorsal pancreatic bud failing to fuse with the ventral bud
• B Ventral pancreatic bud adhering to the duodenal wall during rotation of the stomach and duodenum ✓
• C Accessory dorsal bud arising from the bile duct
• D Failure of canalisation of the main pancreatic duct

Explanation

Annular pancreas arises when the bifid ventral pancreatic bud adheres to the duodenal wall during rotation; the two segments then encircle the second part of the duodenum as they fuse with the dorsal bud, producing constriction. Obstruction here is preampullary, so vomiting is non-bilious, distinguishing it from malrotation volvulus where obstruction is typically postampullary and bilious. Dorsal bud anomalies cause pancreas divisum rather than annular tissue, and duct canalisation failure does not create a constricting ring.

Reference: Langman's Medical Embryology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.