<prompt> A patient with history of choledocholithiasis presents with elevated conjugated bilirubin. Ultrasound reveals a dilated biliary system upto the terminal pa. In case of suspicion of an ampullary obstructive calculus which of the following investigations would be most sensitive?PTCMRCPXray abdomenEndoscpic USG  <response>: EUS- Most sensitive method to detect ampullary stones 