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Colorectal Cancer Health Center

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Colorectal Cancer Screening (PDQ®): Screening - Patient Information [NCI] - Risks of Colorectal Cancer Screening

Screening tests have risks.

Decisions about screening tests can be difficult. Not all screening tests are helpful and most have risks. Before having any screening test, you may want to discuss the test with your doctor. It is important to know the risks of the test and whether it has been proven to reduce the risk of dying from cancer.

Recommended Related to Colorectal Cancer

Understanding Colorectal Cancer -- The Basics

Inside your abdominal cavity is the long, tubular digestive tract. The second part of this tube -- the large intestine -- is composed of the colon, which stretches 4 feet to 6 feet, and the rectum, which is only 4 inches to 6 inches long. The inner lining of this "colorectal tube" can be a fertile breeding ground for small tumors, called polyps (Figure 1). About a quarter of all adults in the U.S. older than age 50 will have at least one colorectal polyp. Most colorectal cancers develop from polyps...

Read the Understanding Colorectal Cancer -- The Basics article > >

False-negative test results can occur.

Screening test results may appear to be normal even though colorectal cancer is present. A person who receives a false-negative test result (one that shows there is no cancer when there really is) may delay seeking medical care even if there are symptoms.

False-positive test results can occur.

Screening test results may appear to be abnormal even though no cancer is present. A false-positive test result (one that shows there is cancer when there really isn't) can cause anxiety and is usually followed by more tests (such as biopsy), which also have risks.

The following colorectal cancer screening tests have risks:

Fecal occult blood testing

The results of fecal occult blood testing may appear to be abnormal even though no cancer is present. A false-positive test result can cause anxiety and lead to more testing, including colonoscopy or barium enema with sigmoidoscopy.


There can be discomfort or pain during sigmoidoscopy. Women may have more pain during the procedure, which may lead them to avoid future screening. Tears in the lining of the colon and bleeding also may occur.


Serious complications from colonoscopy are rare, but can include tears in the lining of the colon, bleeding, and problems with the heart or blood vessels. These complications may occur more often in older patients.

Virtual colonoscopy

Virtual colonoscopy often finds problems with organs other than the colon, including the kidneys, chest, liver, ovaries, spleen, and pancreas. Some of these findings lead to more testing. The risks and benefits of this follow-up testing are being studied.

Your doctor can advise you about your risk for colorectal cancer and your need for screening tests.

    This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http:// cancer .gov or call 1-800-4-CANCER.

    WebMD Public Information from the National Cancer Institute

    Last Updated: May 28, 2015
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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