Serendipitous passage of a common duct stone following ampullary cannulation.

A transduodenal endoscopic pancreatocholangiography dislodged a distal common duct stone. The conclusion that the stone was disimpacted by the manipulation was reached by (1) demonstration of a negative shadow representing a stone in the distal part of the common duct on roentgenograms following injection of contrast material after successful ampullary cannulation, (2) the clinical sequence of events that followed ampullary cannulation, and (3) the operative finding of a grossly dilated common duct without the presence of a stone and normal intraoperative and postoperative T-tube cholangiograms.