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Patient education: Flexible sigmoidoscopy (Beyond the Basics)

Myron Falchuk, MD
Section Editor
John R Saltzman, MD, FACP, FACG, FASGE, AGAF
Deputy Editor
Kristen M Robson, MD, MBA, FACG
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A flexible sigmoidoscopy is an examination of the lower part of the gastrointestinal tract called the colon or large intestine (figure 1). It is performed by an endoscopist, who is a doctor or other health professional with special training in endoscopic procedures. There are several reasons that flexible sigmoidoscopy may be recommended, with one of the most common reasons being the need to screen for colon cancer in people older than 50 years.

Colonoscopy allows the clinician to examine the entire large intestine and is preferred in certain situations. (See "Patient education: Colonoscopy (Beyond the Basics)".)


The most common reasons for flexible sigmoidoscopy are the following:

As a screening test to detect colon polyps or colon cancer (see "Patient education: Colon and rectal cancer screening (Beyond the Basics)")

Blood in the stool or rectal bleeding

Persistent diarrhea

After radiation treatment to the pelvis when a patient has lower gastrointestinal symptoms

Evaluation of the colon in conjunction with a barium enema

For the medical management of colitis (inflammation of the colon)


A healthcare provider will provide specific Instructions about how to prepare for the examination. The instructions are designed to maximize your safety during and after the examination, minimize complications, and allow the endoscopist to easily view the colon.

It is important to read these instructions ahead of time and follow them carefully. Call your clinician or the endoscopy unit if you have questions.

Bowel cleaning — The lower part of the colon must be cleaned to permit the endoscopist to see the inside lining of the colon. You will be given specific instructions, with preparation often including a clear liquid diet, laxatives, and use of an enema shortly before the examination.

Medications — Some medications, such as iron preparations, may need to be stopped one to two weeks before the examination. Iron coats the colon, making it difficult to see the lining. If you take these medications, you should ask your healthcare provider if they need to be stopped before the procedure. People who take a blood thinning medication, such as warfarin (Coumadin), should consult with their clinician regarding the need to stop taking this medication temporarily.

Most medications for high blood pressure, heart disease, lung disease, and seizure disorders are safe during sigmoidoscopy and can be taken the day of the examination.

Medications for diabetes may need to be adjusted before the test; talk to your healthcare provider for advice.


Prior to the sigmoidoscopy, a nurse will ask questions to be sure that you understand the procedure and the reason it is planned. A doctor will review the procedure, including possible complications, and will ask you to sign a consent form.

The procedure — Flexible sigmoidoscopy usually takes between 5 and 15 minutes. It is performed while you lie on your left side with your legs bent like they would be if you were sitting in a chair. The sigmoidoscope, which is approximately the size of one finger, is inserted into the anus and advanced through the rectum, sigmoid colon, and descending colon (figure 1). The sigmoidoscope has a camera and a light source that permits the endoscopist to see the inside of the colon on a television monitor.

The endoscope can be used to take biopsies (small pieces of tissue) and to introduce or withdraw fluid or air. Biopsies do not hurt because the lining of the colon does not sense pain. However, you may feel cramping as air is introduced through the scope and as the scope is passed through segments of the colon. The air is needed to permit the endoscopist to advance the scope and see the lining of the colon.

It is common to feel embarrassed about releasing air through your rectum, although this is recommended to decrease discomfort. Let the endoscopist know if there is discomfort, since air can also be removed through the scope. Because the procedure is brief and discomfort is mild, pain medications or sedation are not routinely used.


Flexible sigmoidoscopy is a safe procedure and complications are rare.

Bleeding can occur from biopsies or the removal of polyps, but this is usually minimal and stops quickly or can be controlled.

The scope can cause a tear or hole in the tissue being examined. This is a serious problem that does not occur commonly.

The following symptoms should be reported immediately:

Severe abdominal pain (not just gas cramps)

A firm, distended abdomen



Bleeding greater than a few tablespoons


Although patients worry about discomforts of the examination, most people tolerate it very well and feel fine afterwards. Most patients are able to return to normal activities, including eating, after the examination. In many cases, you can go to work and drive the same day, provided you did not receive any medications that could interfere with these activities (such as medications used for sedation).

You should contact your doctor about the results of your test and if you have any questions. The endoscopy team will let you know when all the results will be available and if further treatment is necessary.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Colon and rectal cancer screening (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Colonoscopy (Beyond the Basics)
Patient education: Colon and rectal cancer screening (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Overview of colon polyps
Primary sclerosing cholangitis: Inflammatory bowel disease and colorectal cancer
Surveillance and management of dysplasia in patients with inflammatory bowel disease
Evaluation of suspected small bowel bleeding (formerly obscure gastrointestinal bleeding)
Evaluation of occult gastrointestinal bleeding
Screening for colorectal cancer: Strategies in patients at average risk
Screening for colorectal cancer in patients with a family history of colorectal cancer

The following organizations also provide reliable health information.

National Library of Medicine


The American Society of Gastrointestinal Endoscopy


National Digestive Disease Information Clearinghouse



Literature review current through: Nov 2017. | This topic last updated: Tue Jun 30 00:00:00 GMT 2015.
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