Stratification in the gallbladder on intravenous cholangiography. The value of delayed or 24-hour radiographs.

Errors in interpretation of intravenous cholangiograms are often made if 24-hour radiographs are not obtained. Three cases are presented in which radiographs, obtained 1/2--4 hours after administration of contrast material, failed to demonstrate gallstones in the visualized gallbladder. However, 24-hour radiographs revealed calculi in all three patients. Stratification of bile is thought to be the mechanism responsible. Delayed radiographs assure proper mixing of contrast material and bile, and provide optimal visualization of the gallbladder in patients undergoing intravenous cholangiography.