Sigmoidoscopy is an internal examination of the lower large bowel (colon) and rectum, using an instrument called a sigmoidoscope.

Proctoscopy; Proctosigmoidoscopy; Rigid sigmoidoscopy

During the test, you are positioned on your left side with your knees drawn up toward your chest. A gastroenterologist or surgeon will perform the test. First, the doctor does a digital rectal exam by gently inserting a gloved and lubricated finger into the rectum to check for blockage and to dilate (gently enlarge) the anus.

Next, the sigmoidoscope -- a hollow tube through which the doctor can see-- is inserted into the rectum. Air is introduced into the colon to expand the area and help the doctor see better. The air may cause the urge to have a bowel movement.

The sigmoidoscope is advanced, usually as far up as the sigmoid colon or descending colon. Then, as the scope is slowly removed, the lining of the bowel is carefully examined. The hollow channel in the center of the scope allows for the passage of forceps for taking biopsies or for other instruments for therapy.

Sigmoidoscopy may be done using a rigid or flexible scope. Ask your doctor which procedure you are having.

You must sign an informed consent form. You will wear a hospital gown.

On the morning of the procedure, eat a light breakfast and then use a cleansing enema about 1 hour before the sigmoidoscopy.

Infants and children:

The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:

• Infant test or procedure preparation (birth to 1 year)
• Toddler test or procedure preparation (1 to 3 years)
• Preschooler test or procedure preparation (3 to 6 years)
• Schoolage test or procedure preparation (6 to 12 years)
• Adolescent test or procedure preparation (12 to 18 years)

There will be pressure when the scope or fingers are introduced into your rectum. There may be a feeling of the need to have a bowel movement during the procedure. There may be some bloating or cramping caused by the air or by stretching of the bowel by the sigmoidoscope. Biopsies cause no discomfort.

After the test, you will expel the air that was introduced.

This test can help diagnose:

• Bowel obstruction
• Causes of diarrhea
• Colon polyps
• Diverticulosis (the presence of abnormal pouches on the lining of the intestines)
• Inflammatory bowel disease

This test can also be used to:

• Determine the cause of blood, mucus, or pus in the stool
• Confirm findings of another test or x-rays
• Take a biopsy of a growth
• To screen for colorectal cancer

Normal findings show that the lining of the sigmoid colon, rectal mucosa, rectum, and anus appear normal in color, texture, and size.

Abnormal results can indicate:

• Anal fissures
• Anorectal abscess
• Bowel obstruction
• Cancer
• Colorectal polyps
• Diverticulosis
• Hemorrhoids
• Inflammatory bowel disease
• Inflammation or infection (proctitis)

There is a slight risk of bowel perforation (tearing a hole) and bleeding at the biopsy sites (the overall risk is approximately 1 in 1,000).

U.S. Preventive Services Task Force. Screening for colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2008 Nov 4;149(9):627-37.

Weinberg DS. In the clinic. Colorectal cancer screening. Ann Intern Med. 2008 Feb 5;148(3):ITC2-1-ITC2-16.