Health Encyclopedia


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 or abdominal pain
  • Constipation
  • Abnormal growths (polyps)
  • 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 is also a screening test for colorectal cancer.

A sigmoidoscopy is done using a thin, flexible tube (a sigmoidoscope). The tube has a tiny light and camera. The tube is put into your anus and moved slowly through your rectum into the lower part of your colon. The tube will blow air into your colon. This will make it swell up a bit so it is 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 (abdominal) pain
  • Itching around your anus
  • Blood or mucus in your stool

A sigmoidoscopy is one type of test used to screen for colorectal cancer. Health experts recommend that starting at age 50, both men and women follow a colorectal cancer screening schedule. Talk with your healthcare provider about a screening schedule that is best for you.

Your healthcare provider may have other reasons to recommend a sigmoidoscopy.

What are the risks of a sigmoidoscopy?

Problems that may happen with a sigmoidoscopy include:

  • Continued bleeding after biopsy
  • Inflammation of the lining of your abdomen (peritonitis)
  • A hole in (perforation of) your intestinal wall. This is rare.

Some things can interfere with a sigmoidoscopy. These include:

  • Use of soap suds 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, which may not allow a good view of the area

You may have other risks that are unique to you. 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 him or her any questions you have.
  • You will be asked to sign a consent form to do the test. Read the form carefully and ask questions if anything is not clear.
  • You will be given specific instructions about not eating (fasting) or following a special diet before the test.
  • Tell your provider if you are pregnant or think you may be pregnant.
  • Tell your provider if you are sensitive to or allergic to any medicines, latex, tape, and 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.
  • Your doctor will give you instructions 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.
  • If you have a heart valve disease, you may be given disease-fighting medicines (antibiotics) before the test.
  • You usually will not need medicine to help you relax (sedation) or put you into a deep sleep (anesthesia) before the test.
  • Follow any other instructions 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. He or she will also gently enlarge (dilate) your anus.
  5. A greased (lubricated) tube will be slowly put into your anus and moved 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 (an anoscopy) or your anus and rectum (a proctoscopy). If another test is done, then a special tube will be inserted to check your lower rectum or anal canal.
  7. A sigmoidoscopy can cause mild discomfort. But 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 decrease any pain.
  8. Air may be injected 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, tissue samples (biopsies) may be taken 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?

If you were placed in the knee-chest position during the test, you should 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 instructions.

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 (be very flatulent) and have gas pains after the test. This is normal. Walking and moving around may help to ease any mild pain.

Call your healthcare provider if you have any of the following:

  • Fever or chills
  • Bleeding from the rectum that lasts longer than a day
  • Belly (abdominal) pain or swelling
  • Unable to pass gas

Your healthcare provider may give you other instructions, depending on your situation.

Next steps

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

  • The name of the test or procedure
  • The reason you are having the test or procedure
  • The risks and benefits of the test or procedure
  • When and where you are to have the test or procedure and who will do it
  • When and how will you get the results
  • How much will you have to pay for the test or procedure

Medical Reviewers:

  • Kidd, India, RN, BSN, MBA
  • Sohrabi, Farrokh, MD