Concentration and excretion of contrast agents during oral cholecystography as measured by computed tomography in dogs

Nine healthy mongrel dogs were given 2 consecutive doses of 1 of 3 cholecystographic contrast agents (iopanoic acid, sodium ipodate, and sodium tyropanoate), followed by daily computed tomograms (CT) and abdominal radiographs in a randomized crossover study in order to determine: (a) the maximum time for excretion of the contrast material from the gallbladder, (b) the maximum time for elimination of contrast material from the blood, and (c) the correlation between the density of the gallbladder on CT and the actual concentration of iodine in the gallbladder bile. In all 9 animals gallbladder opacification disappeared on CT within 4 days after administration of the contrast material. Plain abdominal radiographs did not show gallbladder opacification after 2 1/2 days. Daily blood iodine measurements showed that all of the contrast material was cleared from the blood within 7 days after administration. In 7 dogs CT imaging of the gallbladder was followed by percutaneous aspiration of bile from the gallbladder using CT guidance. There was a direct linear correlation between the actual concentration of iodine in the bile and the density of the gallbladder on CT (r=0.925). This suggests that CT measurements can be used to determine the concentration of contrast agents in the gallbladder during oral cholecystography.