A barium enema is an x-ray test used to examine the lower digestive tract (the colon and rectum). Because the colon and rectum are normally not visible on x-rays, you need to temporarily coat their inner surfaces with barium, a liquid that does show up on x-rays. This makes the outline of these organs visible on the x-ray pictures. This test is useful for diagnosing cancers and diverticuli (small pouches that may form in the intestinal wall).
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