[Structural differences between biliary calculi overlooked at cholecystectomy or developing later].

Under the common duct stones of cases with cholecystectomy, operated three and more years before, pigment-stones are significantly more frequent than under the cases, which are not operated or operated just before. Cholesterol stones in the common duct after cholecystectomy are almost overlooked stones, but pigment stones often develop after cholecystectomy.