“…Routine operative cholangiography has been advocated in all cholecystectomies because of the incidence of unsus¬ pected common duct stones that ranges between 2% and 4%. [3][4][5] Techniques include cystic duct cholangiograms, chol¬ angiograms via needles in the common bile duct, T-tube cholangiograms, and percutaneous transhepatic chol¬ angiograms." Obstruction to passage of contrast medium into the duodenum may indicate the presence of an ob¬ structing stone or tumor at the ampulla of Vater, but other mechanisms may be operative as well-chiefly, spasm.…”