This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': "Following is an exception to Courvoisier's law: \nSelect and explain. \nA. Cancer of ampulla, B. Cancer of pancreas, C. Cancer of bile duct, D. Primary oriental cholangiohepatitis causing stones in the CBD.", 'role': 'user'}, {'content': "Answer: D \nExplanation: Primary oriental cholangiohepatitis causing stones in the CBD Exceptions to Courvoisier's law: Double impaction - one stone in CBD and stone in cystic duct. Periampullary carcinoma in a patient who has undergone cholecystectomy. Primary oriental cholangiohepatitis causing stones in the CBD (gall bladder is normal in these cases).", 'role': 'assistant'}]