When colorectal cancer is suspected, a variety of tests may be used to make the diagnosis. The physician must first determine that any symptoms are due to cancer and not to another cause. These tests may include a physical exam, a colonoscopy, a sigmoidoscopy, various blood tests, a fecal occult blood test, and biopsies (from tissue taken during the colonoscopy or the sigmoidoscopy). Bleeding from the rectum, and other symptoms of colorectal cancer, may be caused by diverticular disease, inflammatory bowel disease, hemorrhoids, or polyps (the precursors to colorectal cancer).