This examination takes a look at the entire small intestine. The time required for this exam varies greatly from one patient to another, and depends on how actively your intestinal tract is functioning and may be prolonged if there should be some obstruction. You will be given several glasses of barium to drink. X-ray images are taken at varying intervals, from 15 minutes to an hour or more, again depending on the activity of the bowel. The entire examination may take as little as an hour but may well last more than four or five hours. You should follow Prep B very carefully.