A barium enema is a technique to screen the colon for cancer. It uses fluoroscopy to take X rays and image the colon after the radiologist instills barium into the rectum through a small tube.

A newer technique is CT colonography. This is a CT scan of your abdomen and pelvis and afterward the images are computer processed to create 3-D fly-through images of your entire colon that the radiologist uses to look for polyps and tumors.

Both of these procedures require a prep starting the day before with a clear liquid diet and laxatives.

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