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What is a sigmoidoscopy?

A sigmoidoscopy is a diagnostic test to check the lower part of your colon or large intestine (the sigmoid colon). This part of your colon is close to your rectum and anus.

 A sigmoidoscopy can help find out why you have:

  • Diarrhea

  • Belly pain

  • Constipation

  • Abnormal growths (polyps)

  • Rectal bleeding

A sigmoidoscopy may also be used to take a tissue sample or biopsy. And it can be used to remove polyps or swollen veins in your rectum and anus (hemorrhoids). It's also used to screen for colorectal cancer.

A sigmoidoscopy is done using a thin, flexible tube (sigmoidoscope or colonoscope. The tube has a tiny light and camera at one end. It often shows a detailed picture of the inside of your colon. The healthcare provider puts the tube into your anus and moves it slowly through your rectum into the lower part of your colon. Air or carbon dioxide is blown through the tube into your colon. This will make it expand a bit so it's easier to see.

Why might I need a sigmoidoscopy?

A sigmoidoscopy may be used to see or diagnose certain things in your lower colon, such as:

  • Abnormal growths (polyps)

  • Tumors

  • Sores (ulcers)

  • Redness and swelling (inflammation)

  • Swollen veins in your rectum and anus (hemorrhoids)

  • Pouches on your colon wall (diverticula)

  • Narrowing of your lower colon (strictures)

It can also be used to find the cause of recent changes in:

  • Your bowel habits

  • Lower belly pain

  • Itching around your anus

  • Blood or mucus in your stool

  • Low iron levels or low blood count

A sigmoidoscopy is 1 type of test used to screen for colorectal cancer. The American Cancer Society and the U.S. Preventive Services Task Force recommend colorectal cancer screening for people at average risk starting at age 45. Talk with your healthcare provider about a screening schedule that's best for you. Many choices are available to screen for colon cancer.

Your healthcare provider may have other reasons to recommend a sigmoidoscopy. If a sigmoidoscopy shows polyps, then you may need a colonoscopy as the next step to see the rest of the colon.

What are the risks of a sigmoidoscopy?

Problems that may happen with a sigmoidoscopy include:

  • Continued bleeding after biopsy (rare)

  • Inflammation of the lining of your belly (peritonitis) (very rare)

  • A hole in (perforation of) your intestinal wall (rare)

  • Reaction to anesthesia, if given

Some things can interfere with a sigmoidoscopy. These include:

  • Using laxative enemas before the test. These can irritate the lining of your colon.

  • Having barium in your colon from another recent test done to check your colon

  • Not preparing your bowel well before the procedure

  • Problems that may not allow the tube to move. This includes a narrowing of the colon (strictures), surgical scars (adhesions), or a disease, such as chronic inflammatory disease.

  • Rectal bleeding. This may not allow a good view of the area.

You may have other risks. Be sure to discuss any concerns with your healthcare provider before the procedure.

How do I get ready for a sigmoidoscopy?

  • Your healthcare provider will explain the procedure to you. Ask them any questions you have.

  • You will be asked to sign a consent form to do the test. Before you sign, read the form carefully and ask questions if anything is not clear.

  • You will be given specific directions about not eating (fasting) or following a special diet before the test.

  • Tell your provider if you are breastfeeding or pregnant, or think you could be pregnant.

  • Tell your provider if you are sensitive to or allergic to any medicines, latex, tape, or anesthesia medicines (local and general).

  • Tell your provider about all the medicines you take. This includes both over-the-counter and prescription medicines. It also includes vitamins, herbs, and other supplements.

  • Tell your provider if you have a history of bleeding disorders. Let your provider know if you are taking any blood-thinning medicines, aspirin, ibuprofen, or other medicines that affect blood clotting. You may need to stop taking these medicines before the procedure.

  • Tell your provider if you have had any recent illnesses, such as an infection.

  • Your healthcare provider will give you directions on how to prepare your bowel for the test. You may be asked to take a laxative, an enema, or a rectal laxative suppository. Or you may have to drink a special fluid that helps prepare your bowel.

  • You usually will not need medicine to help you relax (sedation) or put you into a deep sleep (anesthesia) before the test. But some providers offer sedation, and some people ask for it.

  • Follow any other directions your provider gives you to get ready.

What happens during a sigmoidoscopy?

You may have a sigmoidoscopy as an outpatient or as part of your stay in a hospital. The way the test is done may vary depending on your condition and your healthcare provider's practices.

Generally, a sigmoidoscopy follows this process:

  1. You will be asked to remove any jewelry or other objects that may interfere with the procedure.

  2. You may be asked to remove clothing. If so, you will be given a gown to wear.

  3. You may be asked to lie on the exam table on your left side with your knees bent towards your chest. Or you may be put in the knee-chest position. This is when you kneel with your head and chest bent down, touching the table.

  4. Your provider will do a rectal exam to check for any blood, mucus, or stool. They will also gently enlarge (dilate) your anus.

  5. Your provider will slowly put a lubricated tube into your anus. Then they will move it into your rectum and the lower part of your colon. After the lower part of your colon is checked, the tube will be removed.

  6. A sigmoidoscopy may be done together with a test to check your anus (anoscopy) or your anus and rectum (proctoscopy). If another test is done, the provider will use a tube to check your lower rectum or anal canal.

  7. A sigmoidoscopy can cause mild discomfort. You may feel a strong urge to have a bowel movement when the tube is inserted. You may also have brief muscle spasms or lower belly pain during the test. Taking deep breaths while the tube is being put in may help ease any pain.

  8. The provider may inject air into your bowel to make it easier to see the area. A suction device may be used to remove liquid stool.

  9. During the test, your provider may take tissue samples (biopsies) from the lining of your large intestine. This will be done using a special brush, forceps, or swab.

  10. If a polyp is seen, it may be removed, biopsied, or left alone until another surgery is done.

  11. After the test is done, the tool will be removed.

What happens after a sigmoidoscopy?

Lie on your side or back for a few minutes before getting up from the table. Move slowly when you stand up. This will help you feel less dizzy from having your head down during the test.

You may go back to your normal diet and activities, unless you have other directions.

If a biopsy or polyp removal was done during the test, you may see a small amount of blood in your bowel movement. This bleeding should stop within a day or so.

You may pass a lot of gas and have gas pains after the test. This is normal. Walking and moving around may help to ease any mild pain.

If you were given sedation, follow your specific directions. This includes not driving yourself home and not working, operating machinery, or making important decisions for 24 hours afterward.

Call your healthcare provider if any of the following occur:

  • Fever or chills

  • Bleeding from the rectum that lasts longer than a day

  • Belly pain or swelling

  • Unable to pass gas

Your healthcare provider may give you other directions.

Next steps

Before you agree to the test or procedure make sure you know:

  • The name of the test or procedure

  • The reason you are having the test or procedure

  • What results to expect and what they mean

  • The risks and benefits of the test or procedure

  • What the possible side effects or complications are

  • When and where you are to have the test or procedure

  • Who will do the test or procedure and what that person’s qualifications are

  • What would happen if you did not have the test or procedure

  • Any alternative tests or procedures to think about

  • When and how will you get the results

  • Who to call after the test or procedure if you have questions or problems

  • How much will you have to pay for the test or procedure

Online Medical Reviewer: Jen Lehrer MD
Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Tara Novick BSN MSN
Date Last Reviewed: 1/1/2023
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