A flexible sigmoidoscopy consists in the passage of a flexible tube, the size of the index finger, through the anus into the rectum and from there into the sigmoid colon. The instrument contains optic fibers that allow the direct examination of the distal 50 cm (or approximately 2 feet) of the large bowel. Sometimes it is connected to a high resolution television monitor.

The entire colon is about 4 to 6 feet long, however about 75% of cancers or polyps are located in these last 2 feet of bowel.

The flexible sigmoidoscopy is not painful, even though it could be described as uncomfortable and it is easily performed in the doctors office. The procedure has a good record of safety; the complications of bleeding or perforation of the bowel occur very rarely. 
In the recent years many primary care physicians, such as internists and general practitioners, have learned the technique and can offer a flexible sigmoidoscopy to their patients. 

In preparation for a flexible sigmoidoscopy the patient should take 2 Fleet phosphate enemas, about 15 minutes apart , in order to cleanse their bowels; the enemas should be retained for 5 minutes each time; this is ideally done about 1 hour prior to the appointment with the doctor. It is not necessary to fast on the day of the exam. 

If a flexible sigmoidoscopy reveals the presence of a polyp then a more complete examination called a colonoscopy should be performed. 

Diagram	Sigmoid Colon