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A sigmoidoscope is a medical instrument used to examine the rectum and sigmoid colon, which is the lower part of the large intestine. Flexible sigmoidoscopes are thin tubes with a light, camera, and channels for air or instruments. Rigid sigmoidoscopes are shorter, straight instruments used for more limited exams. The procedure that uses this instrument is called sigmoidoscopy.
read more about sigmoidoscope ...A sigmoidoscope is used to look for problems in the rectum and lower colon. It can help evaluate rectal bleeding, bowel habit changes, inflammation, polyps, ulcers, tumors, or abnormal screening results. During flexible sigmoidoscopy, a provider may take tissue samples or remove small polyps. The exam does not view the entire colon, so some patients need colonoscopy instead.
A flexible sigmoidoscope is a bendable tube that can travel farther into the sigmoid colon. It usually includes a camera that sends images to a monitor. A rigid sigmoidoscope is a straight instrument used for the rectum and lower sigmoid area. The choice depends on the reason for the exam, the area that needs to be viewed, and the provider’s plan.
The patient is positioned on the exam table, and bowel preparation may be needed so the lower colon is easier to see. The provider inserts the lubricated sigmoidoscope through the anus into the rectum and lower colon. Air or carbon dioxide may be used to open the bowel for better visibility. The provider checks the lining, takes samples if needed, and slowly removes the instrument.
Sigmoidoscopy is generally safe, but it can cause cramping, bloating, bleeding after biopsy, or rare injury to the bowel wall. Patients should follow preparation instructions carefully so the exam is useful. Abnormal findings may lead to biopsy results, treatment, repeat testing, or colonoscopy. Severe abdominal pain, fever, heavy bleeding, or dizziness after the exam needs prompt medical care.
No. A sigmoidoscope checks the rectum and lower colon, while a colonoscope can examine the entire colon.
Usually yes. Preparation may include an enema, laxative, or diet instructions depending on the provider’s directions.
Some small polyps can be removed during flexible sigmoidoscopy. Larger or higher polyps may require colonoscopy.
It can cause pressure, cramps, or bloating. Severe pain is not expected and should be reported during or after the test.
Flexible Sigmoidoscopy: What Is It, Prep & Procedure. Cleveland Clinic. https://my.clevelandclinic.org/health/diagnostics/4953-flexible-sigmoidoscopy. Date Accessed June 15, 2026.
Flexible Sigmoidoscopy. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/flexible-sigmoidoscopy/about/pac-20394189. Date Accessed June 15, 2026.
Flexible Sigmoidoscopy. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/diagnostic-tests/flexible-sigmoidoscopy. Date Accessed June 15, 2026.
Colonoscopy. MedlinePlus. https://medlineplus.gov/colonoscopy.html. Date Accessed June 15, 2026.
Sigmoidoscopy. Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/sigmoidoscopy. Date Accessed June 15, 2026.