Sigmoidoscopy is an examination of the bottom one-third of your large intestine, including your rectum and the bottom part of your colon. To do this exam, your doctor uses a sigmoidoscope—a flexible viewing tube with a light and a lens or video camera on one end, and an eyepiece or video monitor on the other.

Why is the test performed?
Sigmoidoscopy is used to diagnose certain bowel problems such as unexplained bleeding, diarrhea, constipation or rectal pain. If your doctor sees a suspicious area, he can use an attachment at the end of the sigmoidoscope to remove a piece of tissue and send it to the laboratory to be examined under a microscope. This is called a biopsy. If your doctor finds an abnormal area during the test, he or she may recommend a more comprehensive test called a colonoscopy.

Sigmoidoscopy is also used as a screening test to check for colorectal cancer. It usually is done once every 5 years, beginning at age 50. It may be combined with fecal occult blood testing to ensure that cancer is not missed in the upper part of the colon. As an alternative, your doctor may recommend a colonoscopy every 5 to 10 years.

What are the benefits?
The benefits of sigmoidoscopy can include the following: 
• It is often possible to determine the specific cause of symptoms. 
• Conditions such as colitis and diverticulosis can be monitored to determine effectiveness of treatment.
• Polyps and tumors can be discovered at an early stage.

How to prepare for the examination?
To obtain the full benefit of the exam and allow a thorough inspection, the rectum and sigmoid colon must be clean. Preparation usually involves drinking clear liquids the day before along with taking enemas and/or laxatives. Specific instructions for preparation are provided beforehand.

What happens during the procedure?
A sigmoidoscopy usually takes about 15 to 20 minutes to complete. It is generally performed without anesthesia or sedation (giving a tranquilizing medication), though sedatives may be used if you are particularly anxious about the procedure. You will lie on your side on an examining table in a private room, with a sheet draped over your body. The doctor will gently insert the lubricated scope into your rectum, then view the inside of your colon either through the scope itself or on a video monitor attached to the scope. The doctor will use the scope to blow air into your colon to inflate it for a better examination; this may make you feel bloated or like you need to move your bowels.

If a polyp is found in your colon, your doctor may remove a piece of tissue or the entire polyp, using a tool attached to the end of the sigmoidoscope. A sample of the tissue will then be examined under a microscope by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluates cells, tissues, and organs to diagnose disease) to determine if it is cancerous. If polyps are found during the sigmoidoscopy, your doctor will recommend evaluation of the remaining 4 to 5 feet of the colon not visible during a sigmoidoscopy, as there is a higher likelihood of polyps elsewhere in the colon in this circumstance.

Generally, a sigmoidoscopy is uncomfortable but not painful. If it becomes painful, tell the doctor, and the doctor may be able to reposition the scope.

What happens after the exam?
After the exam, the physician explains the findings to the patient and family. If a sedative is given and the affects of the sedatives are prolonged, the physician may suggest an appointment at a later date. If a biopsy has been performed or a polyp removed, the results of these are not
available for three to seven days.

What are the risks?
Bloating and bowel distension are common due to the air inflated into the bowel. This usually lasts only 30 to 60 minutes. If biopsies are done or if a polyp is removed, there may be some spotting of blood. However, this is rarely serious. Other uncommon risks include a diagnostic error or oversight (a small polyp or even a cancer could be missed), or a tear (perforation) of the wall of the colon which might require surgery.