Radiologic evaluation of the large intestine often involves performing a barium enema. This procedure involves introducing barium (an inert substance which has properties which allow it to be visible on x-rays as white) into the rectum through a plastic tube. By filling the large intestine with barium (white on x-rays) one can evaluate several different properties of the bowel. Some of the properties that are examined are the overall size of the lumen (inside hollow space), whether there are any abnormal growths (polyps, cancer) protruding into the hollow organ, or whether there are small projections of the bowel through the bowel wall (diverticuli). This image shows a normal double contrast barium enema.