The main instrument that is used to look inside the colon is the colonoscope, which is a long, thin, flexible tube with a tiny video camera and a light on the end. By adjusting the various controls on the colonoscope, the gastroenterologist can carefully guide the instrument in any direction to look at the inside of the colon. The quality picture from the colonoscope is shown on a TV monitor and gives a clear detailed view. Colonoscopy is more precise than an x-ray.