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Colonoscopy vs. Sigmoidoscopy: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 18, 2023
A colonoscopy examines the entire colon, while a sigmoidoscopy inspects only the lower part, the sigmoid colon.

Key Differences

Colonoscopy and sigmoidoscopy are both procedures that allow doctors to view the inner lining of the large intestine. However, they differ in terms of the extent of the area they cover. A colonoscopy provides a comprehensive view of the entire colon, extending from the rectum to the cecum. This comprehensive view allows physicians to diagnose, treat, and even prevent a wider range of conditions. On the other hand, a sigmoidoscopy restricts its examination to only the lower part of the colon, specifically the sigmoid colon and the rectum.
While both colonoscopy and sigmoidoscopy utilize flexible tubes fitted with cameras to visualize the colon, their scopes and durations vary. A colonoscopy, due to its broader examination range, typically takes longer and might necessitate sedation for the patient's comfort. A sigmoidoscopy, in contrast, is quicker and often performed without sedation, given its limited scope.
When it comes to the purpose behind these procedures, both colonoscopy and sigmoidoscopy serve diagnostic and preventive roles. For instance, they can identify polyps, inflammation, or other abnormalities. Yet, because a colonoscopy examines the entire colon, it is more commonly used for colorectal cancer screenings, whereas a sigmoidoscopy might be utilized when symptoms are localized to the lower colon.
In choosing between colonoscopy and sigmoidoscopy, doctors often weigh the benefits against potential risks and the specific needs of the patient. While a colonoscopy offers a more comprehensive view, it also has a slightly higher risk due to its invasiveness and the sedation involved. Sigmoidoscopy, while less comprehensive, might be preferable for patients with specific symptoms or those at a higher risk from sedation.

Comparison Chart

Scope of Examination

Covers the entire colon.
Examines only the sigmoid colon and rectum.


Longer, due to comprehensive examination.
Typically shorter, given its limited scope.


Often requires sedation.
Generally done without sedation.


Used for broader diagnostic, treatment, and preventive needs.
Primarily diagnostic, especially for lower colon symptoms.


More invasive due to length of colon covered.
Less invasive as it examines a shorter segment of the colon.

Colonoscopy and Sigmoidoscopy Definitions


A medical procedure that examines the entire colon.
My doctor recommended a colonoscopy after I turned 50 for colorectal cancer screening.


A procedure that inspects the rectum and sigmoid colon.
Due to my lower abdominal pain, the doctor suggested a sigmoidoscopy.


A procedure that utilizes a flexible tube with a camera to visualize the entire colon.
To ensure everything was healthy, she underwent a colonoscopy.


An endoscopic procedure to view the inner lining of the sigmoid colon.
To investigate the cause of his symptoms, he had a sigmoidoscopy.


A comprehensive diagnostic tool to view the internal lining of the colon.
Through a colonoscopy, they found the cause of my digestive issues.


A tool to diagnose conditions affecting the rectum and sigmoid colon.
Through a sigmoidoscopy, they identified the source of the bleeding.


A preventive and diagnostic examination of the colon's inner lining.
Regular colonoscopy screenings can help detect colorectal cancer early.


A diagnostic examination of the lower section of the large intestine.
The sigmoidoscopy confirmed the presence of an inflammation.


An endoscopic examination of the full length of the large intestine.
The colonoscopy revealed a few polyps that needed removal.


A short-range diagnostic examination of the large intestine.
She chose a sigmoidoscopy due to its quicker procedure time.


Examination of the colon with a colonoscope. Also called coloscopy.


A tubular instrument used for inspection of the sigmoid colon.


(medicine) The examination of the colon using a colonoscope.


(medicine) Internal examination of the sigmoid colon


Visual examination of the colon (with a colonoscope) from the cecum to the rectum; requires sedation


Visual examination (with a sigmoidoscope) of the lower third of the colon in a search for polyps


Can both procedures detect colon cancer?

Yes, but a colonoscopy provides a broader screening due to its full-colon examination.

What is a colonoscopy?

A colonoscopy is a procedure that examines the entire colon.

How does a sigmoidoscopy differ from a colonoscopy?

A sigmoidoscopy inspects only the sigmoid colon and rectum, whereas a colonoscopy views the entire colon.

Are there risks associated with these procedures?

Both have risks, but they are generally considered safe. A colonoscopy may have slightly higher risks due to its scope and the sedation involved.

Do the procedures cause pain?

Discomfort is possible, but pain is minimized, especially with sedation during a colonoscopy.

Which procedure is more invasive?

Colonoscopy is more invasive due to its comprehensive scope.

Can both procedures treat conditions or only diagnose them?

Both can diagnose and treat certain conditions, like removing polyps.

How long have these procedures been in use?

Both have been used for decades, with techniques evolving over time.

Are there alternatives to these procedures?

Yes, other imaging tests exist, but colonoscopy and sigmoidoscopy provide direct visualization.

Why is bowel preparation necessary?

Clearing the colon ensures accurate visualization and assessment.

Do both procedures use the same equipment?

Both use flexible scopes with cameras, but the length and features might vary.

Is sedation required for both procedures?

Colonoscopy often requires sedation, while a sigmoidoscopy is usually performed without it.

When might a doctor recommend a sigmoidoscopy over a colonoscopy?

A sigmoidoscopy might be preferred when symptoms are localized to the lower colon or if there are concerns about sedation.

How often should one get these procedures?

Recommendations vary, but a colonoscopy is often advised every 10 years for those over 50, while sigmoidoscopy frequency depends on individual circumstances.

How quickly can results be obtained?

Preliminary results are often available immediately, but biopsy results can take longer.

How soon can patients resume normal activities afterward?

Post-sigmoidoscopy, activities can often be resumed immediately. After a colonoscopy, due to sedation, it's advised to rest for the day.

What are the potential complications?

Bleeding, perforation, and adverse reactions to sedation are potential risks, but they are relatively rare.

Are these procedures covered by insurance?

Coverage varies, but preventive screenings, especially colonoscopies, are often covered.

How long does each procedure take?

A colonoscopy typically takes longer than a sigmoidoscopy.

What preparations are needed for both?

Both require bowel prep to clear the colon, but specifics can differ.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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