In some instances conventional radiography may not be able to provide our veterinarians with a diagnosis. In these circumstances it may be necessary to perform contrast radiography. With this technique, a certain contrast material is used to highlight or outline specific structures. One example is the injection of a contrast material into the urinary bladder in patients that may have a bladder tumor that does not show up on conventional radiographs. This tumor may be identified using contrast radiography. Another use of contrast radiography is to evaluate kidney function. The contrast agent is given intravenously and it’s excretion by the kidneys is visualized by taking radiographs. Depending on the degree of excreted contrast material, kidney function may be assessed. This is, for example, important when an animal may have to have one kidney removed, but the veterinarian would like to ensure that the function of the remaining kidney is sufficient.