The digital rectal exam is often feared and has become a go-to joke about toilet humor. In fact, it is a quick and simple test that a physician can use to learn more about what is going on in the rectum.
A digital rectal exam alone is not an effective screening method for colon or rectal cancer; it just doesn't give enough information to the physician. Rectal examinations are often done as part of a routine physical exam, or before a sigmoidoscopy or a colonoscopy.
Before performing a rectal exam, a physician will put on a pair of examination gloves, and use lubricant. He will then inspect the outside of the rectum, which is the anus, and the surrounding skin, or perineal area. Next the physician will insert his finger briefly into the sphincter. He may ask you to bear down as if you were having a bowel movement, or to squeeze (this is to check the muscle tone in the sphincter).
Upon removing his finger from the rectum, the physician will be able to tell if there is any bleeding from the rectum. The entire exam should only take a minute or two, and while a bit uncomfortable, it is usually not painful.
American Cancer Society. "Can Colorectal Polyps and Cancer Be Found Early?." American Cancer Society, Inc 5 Mar 2008. 22 Feb 2013.