The diagnosis of colon cancer is sometimes made following a positive screening test [i.e., digital rectal examination, fecal occult blood test (FOBT), sigmoidoscopy, colonoscopy, or barium enema]. For patients who have symptoms and signs suggestive of colon cancer, the confirmative diagnostic test most commonly performed is colonoscopy with biopsy. Colonoscopy allows direct visualization of the lesion, examination of the entire large bowel for synchronous and metachronous lesions, and an ability to obtain tissue for histologic diagnosis.