Colonoscopy and Other Screening Tests for Colon Cancer


Routine colonoscopies can find colon cancer in its early stages. This screening test allows your doctor to carefully examine your colon for signs of polyps (abnormal growths on the inside surface of the colon that can grow into cancer).

While there are many types of colorectal cancer screening tests, colonoscopy is the only test that can find polyps and remove them. This means that a colonoscopy can both find and prevent colon cancer.

Your care team may recommend other screening tests depending on your personal circumstances.

Below, you can learn about the different types of screening tests for colorectal cancer.

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What is a colonoscopy?

A colonoscopy is a test in which a thin, flexible tube with a light and a video camera on its tip is placed in your colon to search for polyps. It’s the most effective way to find them. Your care team will prescribe a clear-liquid diet and medication to clear out your bowel during the 24 hours before the test. You’ll be sedated during the exam. Your doctor can usually remove any polyps that are detected, which then go to a pathologist (a doctor who specializes in diagnosing disease) for examination and analysis.

Learn more about preparing for a colonoscopy.

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What is a flexible sigmoidoscopy?

A flexible sigmoidoscopy is similar to a colonoscopy. The main difference is that your doctor uses a shorter tube to examine the lower part of your colon.

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What is a virtual colonoscopy?

A virtual colonoscopy (VC) is also known as a CT colonography. VC is an alternate screening option for some people. A radiologist uses CT scan technology to create 2-D and 3-D images of the colon. It does not require sedation. VC has limitations, however. For example, it requires the same preparation as a conventional colonoscopy: a clear-liquid diet and medication to clear out the colon. In addition, if VC detects a polyp or other abnormality in the colon, you may need a colonoscopy to remove it. VC can sometimes miss small or flat polyps.

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What is a fecal occult blood test?

Because colon or rectal bleeding can be a possible sign of colon cancer, a fecal (stool) occult blood test may detect small amounts of blood in your stool that are not otherwise visible. The test works like this: For three consecutive days, you’ll place small stool samples on chemically treated cards. You’ll send those cards to a lab for testing. During this time, you have to follow a special diet to ensure that the test results are accurate. If an abnormality is detected, you may need to have a colonoscopy to remove it.

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What is a fecal immunochemical test?

A fecal immunochemical test (FIT) screens for colon cancer by detecting blood in the stool. Unlike a fecal occult blood test, you don’t have to follow a special diet beforehand. FIT reacts to a part of the hemoglobin molecule (a protein found in red blood cells). If an abnormality is detected, you may need to have a colonoscopy to remove it. FIT is also called an immunochemical fecal occult blood test.

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What is a stool DNA test?

A stool DNA test screens for cancer by looking for gene changes and blood in a stool sample. You do not need to follow a specific diet before submitting a sample. Like other stool tests, if an abnormality is detected, you may need to have a colonoscopy to remove it.

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