This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
A gallstone gets impacted most commonly in which pa of common bile duct 
Select and explain. 
A. Supra duodenal, B. Retro duodenal, C. Ampulla of vater, D. Common hepatic duct
C: Ampulla of vater
Answer: C: Ampulla of vater 
Explanation: Most gallstones pass out of body unnoticed, but some become lodged in the common bile duct, causing jaundice A frequent site of gallstone impaction is the ampulla of vater, where common channel meets the small intestine Blockage of the common channel by a gallstone can induce acute pancreatitis Ref: Internet sources