This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pancreas, Subject name: Surgery
[{'content': '"Double bubble sign" seen in \nSelect and explain. \nA. Annular pancreas, B. Ureterocele, C. Hypertrophic pyloric stenosis, D. Wilm\'s tumour', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Annular pancreas) (1120, 1198-LB) (1137-B & L 25th)Annular pancreas - in which a ring of pancreatic tissue from the head of the pancreas surrounds the descending duodenum X-ray shows a dilated stomach and proximal duodenum (double bubble sign) and little or no air in the rest of the small bowel.Congenital duodenal obstruction - causes of duodenal obstruction are atresia, mucosal web, annular pancreas, preduodenal portal vein and peritoneal bands {Ladd\'s bands) from malrotations - shows - "double bubble sign" (1316-CSDT 11th)', 'role': 'assistant'}]