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
Following is an exception to Courvoisier's law: 
Select and explain. 
A. Cancer of ampulla, B. Cancer of pancreas, C. Cancer of bile duct, D. Primary oriental cholangiohepatitis causing stones in the CBD.
D: Primary oriental cholangiohepatitis causing stones in the CBD.
Answer: D: Primary oriental cholangiohepatitis causing stones in the CBD. 
Explanation: 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).