A colonoscopy involves the insertion of a long, flexible camera into the rectum while someone is under sedation. This camera allows doctors to view the inside of the large intestine, rectum, and part of the small intestine to check for changes or blockages that may be present. A colonoscopy can be either a screening or diagnostic procedure. It is considered screening if you do not have any gastrointestinal symptoms and no polyps or masses are found during the colonoscopy. Screening colonoscopies are recommended every ten years for adults over 45 to prevent colon cancer.