The FOBT detects blood in the stool through a chemical reaction. This test cannot tell
whether the blood is from the colon or from other parts of the digestive tract (such as the
stomach). If this test is positive, a colonoscopy is needed to find the cause of bleeding.
Although cancers and polyps can cause blood in the stool, other causes of bleeding may
occur, such as ulcers, hemorrhoids, diverticulosis (tiny pouches that form at weak spots in the
colon wall), or inflammatory bowel disease (colitis).