Colonoscopy is a procedure where a physician inserts a long thin tube into the colon. This tube is connected to a camera and the physician is able to examine the colon. The doctor is also able to remove small polyps, some of which would otherwise grow into cancerous tumors. Colonoscopy is considered the gold standard for finding and removing -- and possibly preventing – cancers of the colon and rectum. It can detect up to 95% of colon cancers.