You will be asked to lay down on your left side with your knees drawn up toward your chest.
A gastroenterologist or surgeon will usually perform the test.
First, the doctor gently places a gloved and lubricated finger into your rectum to check for blockage and to gently enlarge (dilate) the anus. This is called a digital rectal exam.
Next, a flexible tube called a sigmoidoscope is placed through the anus and gently moved into your colon. This tool has a small camera attached to the end. Air is placed into the colon to open up the area and help the doctor see better. The air may cause the urge to have a bowel movement or pass gas. Suction may be used to remove fluid or stool.
Tissue samples may be taken with a tiny biopsy tool inserted through the scope. Polyps may be removed with heat (electrocautery). Images 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 doctor or nurse will tell you how to prepare for the exam. This includes using a enema to empty your bowels. You usually take this about 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:
Presssure when the scope or fingers are placed into your rectum
Like you 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 introduced.
Children may be sedated for this procedure.
Why the test is performed
This test can help diagnose the cause of:
Diarrhea, constipation, or other changes in bowel habits
There is a slight risk of bowel perforation (tearing a hole) and bleeding at the biopsy sites (the overall risk is less than 1 in 1,000).
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George F Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.