Colonoscopy is a visual examination of the lining of your large bowel (colon) with sedation. A flexible tube (about the thickness of the little finger) is passed through the rectum and around the colon. A small video camera, which can take photos, sends an image onto a video screen. The doctor looks for any abnormalities and if necessary, biopsies (small tissue samples) can be painlessly taken through the colonoscope using tiny forceps. These biopsies are examined under a microscope in the laboratory. Polyps (abnormal growths of tissue) can be removed with biopsy forceps or cold snaring and large polyps are removed using a diathermy snare. This is done by passing a wire loop, like a lasso, over the polyp. The polyp is cut from the bowel lining using electrical current, which seals the tissue and stops bleeding. This current cannot be felt and causes no pain.