During a colonoscopy, a long, flexible tube (colonoscope) is inserted into the rectum. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon. If necessary, polyps or other types of abnormal tissue can be removed through the scope during a colonoscopy. Tissue samples (biopsies) can be taken during a colonoscopy as well. This test can also be done to check for cancerous growths in the colon of rectum. Before a colonscopy, you will need to prep for 1 to 2 days. This is a clear liquid diet that will cause you to use the bathroom often.