This is an examination of your large intestine. To get a high quality examination, your bowel must be completely cleaned out. To do this it is very important that you follow Prep C to the letter, no more and no less. The examination involves placing the tip of an enema tube into your rectum. The tip has a balloon on it, which will help you hold the material. A barium mixture will then flow into the rectum, filling the entire large bowel. In most cases, air will be used to push the barium along and to distend the bowel. A series of x-ray images will be taken.