It starts at the cecum, which attaches to the end of the small intestine, and it ends at the rectum and anus. The colon is a hollow tube, about five feet long, and its main function is to store unabsorbed food products prior to their elimination. 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 high 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.
This procedure also allows other instruments to be passed through the colonoscope. In this way, colonoscopy may help to avoid surgery or to better define what type of surgery may need to be done. A shorter version of the colonoscope is called a sigmoidoscope, an instrument used to screen the lower part of the large bowel only. The colonoscope, however, is long enough to inspect all of the large bowel and even part of the small intestine. Colonoscopy is a safe and effective way to evaluate problems such as blood loss, pain, and changes in bowel habits such as chronic diarrhea or abnormalities that may have first been detected by other tests.