Floating gallstones: the role of contrast material.

Among more than 400 patients with gallstones examined in our department in the past 2 yr, calculi were seen to float in only 3 patients. In each of these cases the ultrasound examination was done during or shortly after the oral cholecystogram. This suggests that contrast material raised the specific gravity of the bile and caused the floating phenomenon. No cases of floating stones in the absence of contrast material were found.