This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gall Bladder & Bile Ducts, Subject name: Surgery
All are true bout CBD stones except: 
Select and explain. 
A. Associated with GB stones in 10% cases, B. Primary stones are usually brown, C. Laboratory values may be normal in one third cases of choledocholithiasis, D. Retained stones are discovered after 2 years of cholecystectomy
D: Retained stones are discovered after 2 years of cholecystectomy
Answer: D: Retained stones are discovered after 2 years of cholecystectomy 
Explanation: Ans. (d) Retained stones are discovered after 2 years of cholecystectomy* Recurrent stone: discovered after 2 years after Cholecystectomy* Retained stone: discovered within 2 years after cholecystectomy