Flexible sigmoidoscopy enables the physician to look at the inside of the large intestine from the rectum through the last part of the colon, called the sigmoid or descending colon. Physicians may use the procedure to find the cause of diarrhea, abdominal pain or constipation. The test can be used to look for early signs of cancer in the descending colon and rectum. With flexible sigmoidoscopy, the physician can see bleeding, inflammation, abnormal growths and ulcers in the descending colon and rectum. Flexible sigmoidoscopy is not sufficient to detect polyps or cancer in the ascending or transverse colon (two-thirds of the colon).

For the procedure, the patient lies on the left side on the examining table. The physician inserts a short, flexible, lighted tube into your rectum and slowly guides it into your colon. The tube is called a sigmoidoscope. The scope transmits an image of the inside of the rectum and colon, the physician can carefully examine the lining of these organs. The scope blows air into these organs, which inflates them and helps the physician see better.

If anything unusual is in your rectum or colon, like a polyp or inflamed tissue, the physician can biopsy it using instruments inserted into the scope. The physician sends that piece of tissue (biopsy) to the lab for testing.

Bleeding and puncturing of the colon are possible complications of sigmoidoscopy. However, such complications are uncommon.

Flexible sigmoidoscopy takes 10-20 minutes. During the procedure, the patient might feel pressure and slight cramping in the lower abdomen. The patient feels better when the air leaves the colon.

Preparation
The colon and rectum must be completely empty for flexible sigmoidoscopy to be thorough and safe, the physician tells the patient to drink only clear liquids for 12-24 hours before the procedure. A liquid diet means fat-free bouillon or broth, gelatin, strained fruit juice, water, plain coffee, plain tea or diet soda. The night before or right before the procedure, the patient is given an enema, which is a liquid solution that washes out the intestines. Your physician may give you other special instructions.