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
"Double bubble sign" seen in 
Select and explain. 
A. Annular pancreas, B. Ureterocele, C. Hypertrophic pyloric stenosis, D. Wilm's tumour
A: Annular pancreas
Answer: A: Annular pancreas 
Explanation: (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)