A barium enema is a special X-ray of the colon and rectum. The colon and rectum are also called the large bowel.

The bowel doesn’t show up well on normal X-rays. To make better pictures, a substance called barium is put into the bowel.

The barium coats the inside of the bowel and makes it easier to see on the X-rays. Radiological images are created by passing small, highly controlled amounts of radiation through the body and capturing the resulting shadows and reflections on film.