<prompt> The treatment of choice for an 8 mm retained common bile duct CBD stone isLaparoscopic CBD explorationPercutaneous stone extractionEndoscopic stone extractionExtracorporeal shock wave lithotripsy  <response>: For CBD stones, endoscopic papillotomy is the preferred first technique with a sphincterotomy, removal of stones using Dormia basket or balloon catheter.ERCP can be used to remove retained CBD stones in 3 weeks of surgery. Reference: SRB;s manual of surgery,5th edition, page no:652. 