Colonoscopy allows the physician to examine the entire colon and often the lower portion of the small intestine. The gastroenterologist uses a flexible instrument longer than the sigmoidoscope, which he introduces into the rectum and advances through the colon. This procedure takes longer than a sigmoidoscopy and generally requires the use of anti-pain and sedative medications, given by intravenous injection. In order for your doctor to have a clear view during a sigmoidoscopy or colonoscopy, your colon must be completely free of stool prior to the exam. Therefore, you must carefully and accurately follow the special instructions regarding diet, laxatives, and, at times, enemas prior to these procedures.
Upper endoscopy is performed with a thin, flexible tube that is passed through the mouth.
It allows the physician to determine whether there is inflammation or ulceration of the stomach and upper intestine. The physician may spray the back of your throat with an anesthetic to numb the throat and prevent gagging, or he may administer intravenous sedatives. In order for the physician to have a clear view of your upper digestive tract, your stomach must be completely empty. This generally requires that you fast for at least eight to 12 hours before the exam, and that you avoid any lozenges, hard candy, and antacids that coat and discolor the lining of the esophagus.