Why is it necessary to retrieve small bile duct stones at cholecystectomy?

Recovery of gallstones from the stool demonstrates that gallstones pass into the duodenum due to antegrade sphincter of Oddi (SO) activity. However, retrograde SO peristalsis occurs in three-fourths of patients with bile duct stones as shown by SO manometry. The aim of this study was to investigate, by comparing patients with and without bile duct stones, whether reversed SO activity would retain even small stones. Thirty-nine patients with gallbladder stones < or = 3 mm in diameter underwent cholecystectomy, 22 of them with concomitant biliary stones. The remaining 17 patients served as controls. The diameters of the cystic duct and the small stones in the gallbladder and bile duct were measured. The case histories of the controls indicated previous passage of gallstones into the duodenum, i.e., a normal antegrade SO activity. Biliary stones < or = 3 mm in diameter were recovered in three-fourths of the patients with ductal stones, a sign of retrograde SO activity. SO dysfunction seems to occur in three-fourths of patients with bile duct stones and should be suspected when stones < or = 3 mm are present, as, under these circumstances, it is necessary to retrieve even such small stones.