There are various screening tests that can be performed. One of the more common tests is called fecal occult blood testing, which involves testing the stool to detect any blood that might not be visible to the naked eye. Since it only detects cancers and polyps that are bleeding at the time of the test, however, fecal occult blood testing is typically used in conjunction with other screening techniques. Flexible sigmoidoscopy is performed in the office, and allows your doctor to look directly at the lining of the colon and rectum. The test focuses on the lining of the lower one-third of the colon and rectum, where many polyps and cancers typically reside. Combined with fecal occult blood testing, flexible sigmoidoscopy can detect many cancers and polyps. If a flexible sigmoidoscopy results in the detection of a polyp or cancer, or if a patient is considered at a higher risk for developing colorectal cancer, then the doctor will likely perform a colonoscopy. This procedure allows for a full visual examination of the colorectal lining, in order to diagnose problems and to perform biopsies and to remove polyps. Colonoscopies are typically performed on an outpatient basis, and involve very little discomfort. Barium enema, or x-ray of the colon, is another procedure used to detect large polyps or tumors. It is less accurate for smaller tumors, and not quite as effective as a colonoscopy.