A barium enema is performed to examine the walls of the colon. During the procedure, a well lubricated enema tube is inserted gently into the rectum. The barium, a radiopaque (shows up on X-ray) contrast medium, is then allowed to flow into the colon. The flow of the barium is monitored by the health care provider on an X-ray fluoroscope screen (like a TV monitor). The test is used to detect colon cancer. The barium enema may also be used to diagnose and evaluate the extent of inflammatory bowel diseases.