It is done with a lighted, flexible, hollow tube, which is about the thickness of a finger. The sigmoidoscope is inserted into the anus through the rectum and into the large intestine . Using the sigmoidoscope, the doctor can see whether polyps or cancer are present. At the time of sigmoidoscopy, a biopsy forceps may be inserted through a channel of the scope to remove a small sample of tissue for microscopic examination. Sometimes it is necessary for the doctor to introduce air into the sigmoid colon to improve visibility.
Most patients feel a little cramping or discomfort when having a flexible sigmoidoscopy.
Before having a sigmoidoscopy the colon must be clear of stool so that the doctor has good visibility. The patient must undergo a preparation that may include a liquid diet, enema, and laxatives to clear stool from the colon. The technique for bowel preparation may differ by health facility. A colonoscopy is an examination of the rectum and the entire colon. It is performed with a lighted, flexible, hollow tube, which is slightly larger in diameter than an enema tube.