Flexible sigmoidoscopy is similar to colonoscopy examination except that only the rectum and lower part of the large bowel is examined. This examination requires no sedation, as well as a limited preparation as opposed to the colonoscopy examination. Patients should be given 1–2 enemas prior to the procedure but may also take laxatives or alter their diet on the day prior to the examination. During the procedure he or she will lie on the left side and a small flexible tube about the size of one's finger will be placed in the colon and passed up to sixty centimeters, just below the splenic flexure of the colon. Biopsies can be obtained and polyps can be removed. Stool studies can be obtained as well for further investigation.
Flexible sigmoidoscopy is not a substitute for colonoscopy in terms of screening for colon cancer, because sigmoidoscopy examines only one third of the colon at most. If polyps are seen in the colon the patient may be asked to undergo further investigation with colonoscopy. Following the procedure, if there is no sedation given, the patient may return to work or is free to leave on his own without accompaniment.