In oral cholecystography, an iodinated contrast agent such as iopanoic acid (Telepaque) is given orally the day before the examination.[83] The contrast agent is absorbed from the gut, taken up by the liver, conjugated with glucuronic acid, and secreted into bile, where it is concentrated in the gallbladder. It is still useful in patients who have suspected gallbladder symptoms but a negative or equivocal ultrasound examination. On oral cholecystography the gallbladder may be seen to contain stones, polyps, or sludge, or it may simply not be visualized because contrast material is reabsorbed through an inflamed gallbladder wall or because the cystic duct is obstructed.[84]