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IMAGE Just talking about a colonoscopy makes most people cringe. That is probably because the idea of having a tube inserted into your rectum and colon is disturbing. The thought of getting colorectal cancer is even more disturbing. But, the chances of survival are high when diagnosed before the cancer has invaded the colon wall or spread.

What about colorectal screening? Is the unpleasant prospect of having a colonoscopy or some other equally disagreeable procedure really worth it? For many of us, the answer is “yes.”

Screening Tests: What Do They Entail?

Colorectal screening tests are designed to detect cancer or finger-like projections of tissue called polyps. Polyps may be cancerous or precancerous. Although most polyps are not cancerous, the vast majority of colorectal cancers are believed to begin as polyps. Here is what is involved with each screening test to detect polyps and colorectal cancer:

Fecal Occult Blood and Fecal Immunochemical Tests

The fecal occult blood test and fecal immunochemical test look for hidden blood in a sample of stool (feces) you have already passed. Blood in your feces may be the result of bleeding from a cancerous polyp in your colon or rectum, or it may be a sign of a more benign condition.

Flexible Sigmoidoscopy

For a flexible sigmoidoscopy, a thin, lighted tube with a camara on the end is inserted into the rectum and lower colon to examine their internal mucosal lining. Images can be recorded while the doctor looks for polyps and other abnormalities on a monitor. This procedure does not look at the entire length of the colon like a colonoscopy does.


For a colonoscopy, a thin tube similar to a flexible sigmoidoscope is used. This time, the lighted tube goes all the way through to the end of your colon where it connects to the small intestine. Polyps that are detected can be removed during the procedure.

Double-Contrast Barium Enema

A double-contrast barium enema involves the injection of a fluid called barium followed by air into your rectum. This makes your entire colon visible on an x-ray, allowing doctors to see abnormal growths, like polyps.

CT Colonography

CT colonography is a technique that takes computer generated x-ray images after injection of air into the colon. One disadvantage to having this test compared to a colonoscopy is if a polyp is discovered during colonoscopy it can be removed right then and there, while if one is detected with virtual colonoscopy, a follow-up colonoscopy will be necessary.

MR Colonography

An MR colonography uses magnetic fields to view the entire colon. Water and contrast material are used to expand and view the colon. Compared to conventional colonoscopy, MR colonongraphy is not as effective at detecting smaller polyps.

Screening Recommendations

The American Cancer Society suggests that starting at age 50, men and women at average risk of developing colorectal cancer should use one of the following options:

  • Colonoscopy every 10 years
  • Flexible sigmoidoscopy every 5 years
  • CT colonography every 5 years
  • Double-contrast barium enema every 5 years
  • Annual fecal occult blood test (FOBT)
  • Annual fecal immunochemical test (FIT)

However, people at increased risk of colorectal cancer may need to have some of these tests earlier in life and more often. Some reasons why you would be considered high risk are:

  • Personal or family history of colorectal cancer or adenomatous polyps
  • Personal history of chronic inflammatory bowel disease, such as ulcerative colitis or Crohn's disease

What Tests Do You Need?

Talk to your doctor about the advantages and disadvantages of each screening test, especially if your risk for colorectal cancer is greater than average. These tests may save your life.

  • American Cancer Society


  • National Cancer Institute


  • Canadian Cancer Society


  • Colon Cancer Canada


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  • Colorectal cancer prevention and treatment. American Gastrenterological Association website. Available at http://www.gastro.org/patient-center/digestive-conditions/colorectal-cancer. Accessed July 11, 2012.

  • Colorectal cancer screening tests. American Cancer Society website. Available at: http://www.cancer.org/Cancer/ColonandRectumCancer/MoreInformation/ColonandRectumCancerEarlyDetection/colorectal-cancer-early-detection-screening-tests-used. Updated June 15, 2012. Accessed July 11, 2012.

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  • Screening for colorectal cancer. United States Preventive Services Task Force website. Available at http://www.uspreventiveservicestaskforce.org/uspstf/uspscolo.htm. Updated March 2009. Accessed July 11, 2012.

  • 4/8/2014 DynaMed's Systematic Literature Surveillance. http://www.ebscohost.com/dynamed: Yee J, Kim DH, et al. Colorectal cancer screening. American College of Radiology (ACR) Appropriateness Criteria. Available at: http://www.acr.org/~/media/ACR/Documents/AppCriteria/Diagnostic/ColorectalCancerScreening.pdf. Updated 2013.