Sigmoidoscopy is a procedure used to see inside the sigmoid colon and rectum. The sigmoid colon is the area of the large intestine nearest to the rectum.
How the Test is Performed
During the test:
- You lie on your left side with your knees drawn up to your chest.
- The doctor gently places a gloved and lubricated finger into your rectum to check for blockage and gently enlarge (dilate) the anus. This is called a digital rectal exam.
- Next, the sigmoidoscope is placed through the anus. The scope is a flexible tube with a camera at its end. The scope is gently moved into your colon. Air is inserted into the colon to enlarge the area and help the doctor view the area better. The air may cause the urge to have a bowel movement or pass gas. Suction may be used to remove fluid or stool.
- The doctor may take tissue samples with a tiny biopsy tool inserted through the scope. Heat (electrocautery) may be used to remove polyps. Photos of the inside of your colon may be taken.
Sigmoidoscopy using a rigid scope may be done to treat problems of the anus or rectum.
How to Prepare for the Test
Your health care provider will tell you how to prepare for the exam. You will use an enema to empty your bowels. This is usually done 1 hour before the sigmoidoscopy.
On the morning of the procedure, eat a light breakfast.
How the Test will Feel
During the exam you may feel:
- Pressure during the digital rectal exam or when the scope is placed in your rectum.
- The need to have a bowel movement.
- Some bloating or cramping caused by the air or by stretching of the bowel by the sigmoidoscope.
After the test, your body will pass the air that was put into your colon.
Children may be given medicine to make them sleep lightly (sedated) for this procedure.
Why the Test is Performed
Your doctor may recommend this test to look for the cause of:
- Abdominal pain
- Diarrhea, constipation, or other changes in bowel habits
- Blood, mucus, or pus in the stool
- Weight loss that can't be explained
This test can also be used to:
- Confirm findings of another test or x-rays.
- Screen for colorectal cancer or polyps.
- Take a biopsy of a growth.
A normal test result will show no problems with the color, texture, and size of the lining of the sigmoid colon, rectal mucosa, rectum, and anus.
What Abnormal Results Mean
There is a slight risk of bowel perforation (tearing a hole) and bleeding at the biopsy sites. The overall risk is very small.
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Review Date 8/1/2015
Updated by: Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Internal review and update on 09/01/2016 by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.