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
Ramu, presents with recurrent attacks of cholelithiasis, U/S examination shows a dilated CBD of 1 cm. The next line of management is - 
Select and explain. 
A. ERCP, B. PTC, C. Cholecystostomy, D. Intravenous cholangiogram
A: ERCP
Answer: A: ERCP 
Explanation: The first inv. for any pt. with cholelithiasis or jaundice is U/S.
Next inv. depends on U/S findings,
If the intrahepatic ducts are dilated without any extrahepatic dilatition
then the preferred inv. is → PTC
If the dilatation is in CBD → ERCP.
ERCP may provide direct diagnosis of the distal CBD pathology and may be therapeutic as well for a C stone or stricture.