Direct comparison
Sigmoidoscope vs Colonoscope: Reach and Use
Sigmoidoscope vs colonoscope: how far each flexible scope reaches, sedation and prep per NIDDK, and how 21 CFR 876.1500 lists both. Not medical advice.
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How do Sigmoidoscope, Colonoscope compare side by side?
The table below compares Sigmoidoscope, Colonoscope across 11 procurement-relevant dimensions, from what the instrument is through source.
Side-by-side comparison
| Dimension | Sigmoidoscope | Colonoscope |
|---|---|---|
| What the instrument is | A flexible tube with a camera on one end, called a sigmoidoscope or scope. | A flexible tube with a camera on one end, called a colonoscope or scope. |
| Part of the bowel it is used to look at | The rectum and the lower colon, which includes the sigmoid colon and descending colon. | The rectum and the colon; NIDDK notes it shows the entire colon. |
| Procedure it is used in | Flexible sigmoidoscopy. | Colonoscopy. |
| Relative time | The procedure usually takes about 10 to 20 minutes, and NIDDK says it may take less time than a colonoscopy. | Takes longer than a flexible sigmoidoscopy, per NIDDK; recovery at the hospital or outpatient center is about 30 to 60 minutes afterward. |
| Sedation described by NIDDK | Typically no sedatives or anesthesia needed. | A health care professional places an IV to give sedatives, anesthesia or pain medicine. |
| Bowel preparation described by NIDDK | Often requires less bowel prep than colonoscopy. | More bowel prep than a flexible sigmoidoscopy, per NIDDK’s comparison. |
| If polyps or abnormal tissue are seen | The doctor may remove polyps during the procedure, or may recommend a colonoscopy to examine the rest of the colon. | Used to examine the rest of the colon when a flexible sigmoidoscopy finds polyps or other abnormal tissue. |
| Role in colorectal cancer screening | NIDDK says doctors rarely use it as a screening tool for colon polyps and colorectal cancer. | NIDDK says doctors may recommend it for screening because it shows the entire colon. |
| Device regulation | Listed by name as a sigmoidoscope among the examples of the endoscope generic type in 21 CFR 876.1500. | Listed by name as a colonoscope among the same examples in 21 CFR 876.1500. |
| Which one is used | Decided by the treating doctor. The instrument-level difference is shorter reach: rectum and lower colon only. | Decided by the treating doctor. The instrument-level difference is full reach: rectum and the entire colon. |
| Source | NIDDK flexible sigmoidoscopy page (niddk.nih.gov/health-information/diagnostic-tests/flexible-sigmoidoscopy, last reviewed 2024-07-01, read 2026-10-30); 21 CFR 876.1500, Endoscope and accessories (law.cornell.edu/cfr/text/21/876.1500, read 2026-10-30). | NIDDK colonoscopy page (niddk.nih.gov/health-information/diagnostic-tests/colonoscopy, last reviewed 2023-08-01, read 2026-10-30); 21 CFR 876.1500, Endoscope and accessories (law.cornell.edu/cfr/text/21/876.1500, read 2026-10-30). |
Common questions
Common questions about Sigmoidoscope vs Colonoscope
What is the difference between an endoscopy and a flexible sigmoidoscopy?
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Endoscope is the broad device type: under 21 CFR 876.1500 it is a device that provides access, illumination and observation of body cavities, hollow organs and canals, and the regulation lists sigmoidoscopes, colonoscopes, proctoscopes and anoscopes among its examples. Flexible sigmoidoscopy is one specific procedure that uses one of those instruments: NIDDK describes a doctor using a flexible tube with a camera, called a sigmoidoscope, to look inside the rectum and lower colon.
What is a sigmoid colonoscopy used for?
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"Sigmoid colonoscopy" mixes two separate names. The procedure that looks at the sigmoid colon is flexible sigmoidoscopy, which NIDDK says can show irritated or swollen tissue, ulcers, polyps and cancer in the rectum and lower colon, and which doctors rarely use as a colorectal cancer screening tool. A colonoscopy uses a colonoscope to look at the rectum and the entire colon.
Why have a sigmoidoscopy instead of a colonoscopy?
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NIDDK gives these reasons a flexible sigmoidoscopy can be attractive: it may take less time, you may not need sedatives or anesthesia, and it often requires less bowel prep. The trade-off is reach: a colonoscopy shows the entire colon, and NIDDK says a doctor may recommend one if polyps or abnormal tissue are found during a sigmoidoscopy. The choice is made with your doctor.
How does a proctoscope compare with a sigmoidoscope?
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21 CFR 876.1500 lists proctoscopes and sigmoidoscopes as separate named examples of endoscopes. For the proctoscope and anoscope side of the comparison, see the CASRAI guide to the anoscope.
Going deeper
