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: Surgery
[{'content': 'A patient with a history of choledocholithiasis presents with elevated conjugated bilirubin. Ultrasound reveals a dilated biliary system up to the terminal pa. In case of suspicion of an ampullary obstructive calculus which of the following investigations would be most sensitive? \nSelect and explain. \nA. PTC, B. MRCP, C. X-ray abdomen, D. Endoscopic USG', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Endoscopic USG - Most sensitive method to detect ampullary stones. EUS sensitivity of 93.7% to detect choledocholithiasis. Magnetic resonance cholangiopancreatography (MRCP) is also highly sensitive (>90%) with an almost 100% specificity for the diagnosis of common duct stones.Advantages of EUS is it can be followed up with ERCP immediately.An advantage of MRCP is completely non-invasiveSabiston 20th edition pg 1521', 'role': 'assistant'}]