Oral cholecystography: osmotic activity of iopanoic glucuronide in bile

The cholecystographic agent iopanoic acid (Telepaque) is excreted in high concentrations in the bile as the glucuronide, but produces little or no choleresis. In order to determine the osmotic characteristics of the excretory product, bile was collected from treated and untreated anesthetized dogs and the major solute concentrations and biliary osmolality were determined. After iopanoic acid, there was no change in biliary osmolality or in chloride or bicarbonate concentration. However, the calculated osmolality exceeded the measured osmolality to a significant degree. The data suggest that iopanoic glucuronide, like bile salts, is osmotically inactive because of micelle formation. From physiological considerations, low osmotic activity of the excreted contrast agent might enhance radiographic quality.