Unless colon polyps are large and cause bleeding or pain, the only way to know if you have polyps is to have one or more tests that explore the inside surface of your colon.

Several tests can be used to detect colon polyps. Two of these exams, flexible sigmoidoscopy and colonoscopy, also can be used to collect tissue samples (called a biopsy) or to remove colon polyps. All the tests may be used to screen for colon polyps and colon cancer and as follow-up tests after colon polyps have been removed. These tests include:

• Fecal occult blood test (FOBT). A fecal occult blood test (FOBT) is done to look for microscopic amounts of blood in stool. FOBT is a simple, low-cost screening tool for colon polyps or colon cancer. FOBT has been shown in studies to reduce the number of deaths from colon cancer.¹ By itself, an FOBT is not evidence of colon polyps or colon cancer, and a negative FOBT (no blood found) does not mean that you do not have colorectal cancer. If a fecal occult blood test is positive for blood in the stool, it is important to have a colonoscopy to help your doctor find the source of the blood and remove polyps if they are found.
• Flexible sigmoidoscopy. Flexible sigmoidoscopy allows the doctor to look at the lower third of the colon. During a sigmoidoscopy exam, samples of any growths can be collected (biopsied), and precancerous and cancerous growths can sometimes be removed. Although a sigmoidoscopy does not cover the entire colon, a study has found that when combined with an FOBT, it can detect about 76% of advanced colon polyps or cancers.²
• Colonoscopy. This screening method allows a doctor to inspect the entire colon for polyps and cancer. During a colonoscopy, samples of any growths can be collected (biopsied), and precancerous and cancerous growths sometimes can be removed. Expert groups recommend having the test every 10 years beginning at age 50 for people who are at average risk of colon cancer or whenever another screening test is positive for possible colon polyps or cancer. Screening may begin earlier and be more frequent in people at higher risk for colon polyps and colon cancer.³
• Double-contrast barium enema (DCBE). This exam, also known as a lower gastrointestinal (GI) exam, is an X-ray of the large intestine. A double-contrast barium enema can be used to screen for colon cancer because it can detect polyps in the entire colon. A DCBE can more accurately detect large polyps and cancer than a fecal occult blood test combined with flexible sigmoidoscopy. However, a DCBE is not as accurate as a colonoscopy. DCBE also may miss smaller polyps, may incorrectly identify stool as a polyp, and does not allow the doctor to obtain a biopsy or remove polyps.