Patient Education2 min read

Flexible Sigmoidoscopy

Overview

In a flexible sigmoidoscopy, a doctor passes a thin, flexible tube with a light and camera (a sigmoidoscope) through the anus to look at the inside of the rectum and the sigmoid colon, the lower part of the large bowel. It looks at about the last third or less of the colon, unlike a full colonoscopy, which examines the whole colon. Small tissue samples (biopsies) can be taken during the test.

Who needs it

People with rectal bleeding or blood in the stool that needs a cause found

People with ongoing diarrhoea or a change in bowel habit

People with ulcerative colitis or Crohn’s disease, to judge activity or response, or when severe colitis needs a quick look

Selected people when a limited examination is suitable, or when a full colonoscopy is not possible

Risks

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Bloating, gas and cramping for a short time (common)

•

Minor bleeding, especially after a biopsy or polyp removal (usually stops by itself)

•

Rarely, a tear (perforation) in the bowel wall that may need hospital treatment or surgery

•

Rarely, a reaction to sedation, if used

•

Go to the emergency department promptly if, after the test, you have severe or increasing belly pain, a swollen hard belly, fever or chills, heavy bleeding or clots, black stools, dizziness or fainting.

Before the procedure

Tell the team about all your medicines, especially blood thinners (warfarin, apixaban, rivaroxaban, clopidogrel, aspirin) and diabetes medicines, and do not stop them unless you are told to.

Tell the team about allergies, pregnancy, heart or lung conditions, or previous bowel surgery.

You can usually eat lightly and drink as normal unless told otherwise. Follow your unit’s instructions on food and drink.

Many people have it without sedation. If sedation is planned, arrange for an adult to take you home.

When to See a Doctor

Call your doctor or go to emergency if after the procedure you have severe or worsening abdominal pain, fever, repeated vomiting, heavy bleeding, black stools or fainting.

Why it is done

It helps find the cause of rectal bleeding, diarrhoea, changes in bowel habit or pain in the lower bowel, check how active ulcerative colitis or Crohn’s disease is, look for inflammation after treatment, and detect polyps or growths in the lower colon. If something important is found, you may need a full colonoscopy.

During the procedure

You lie on your left side with your knees drawn up. The doctor checks the area and gently passes the lubricated scope. Air or carbon dioxide gas is gently put in to open the bowel so it can be seen, which may cause cramping, pressure or a feeling that you need to pass stool. Slow breathing helps. The test usually takes about 10 to 20 minutes. If a small polyp or inflamed area is found, a biopsy or removal may be done; this is usually painless.

After the procedure

Most people go home soon after. You may feel wind, bloating or mild cramps for a short time; passing the gas helps. A little blood-streaking of stool after a biopsy can occur. If you had sedation, do not drive, sign legal papers or make important decisions for the rest of the day. You can usually eat and return to normal activity soon, unless told otherwise. Your doctor will explain what was seen, and biopsy results usually take a few days to a couple of weeks.

When you get the results

You will usually hear what the doctor saw on the same day. Biopsy results generally take several days to a couple of weeks, and your doctor will explain what they mean and whether you need more tests, such as a full colonoscopy.

Alternatives

Alternatives include a full colonoscopy, which looks at the whole colon, CT colonography (a scan of the colon), stool tests for blood or inflammation, or imaging such as MRI, depending on the question. Each has pros and cons; for example, scans and stool tests cannot take biopsies. Your doctor will explain which is best for you.

Questions to ask your doctor

• Why do I need this test rather than a full colonoscopy?

• How do I prepare, and do I need an enema or a laxative?

• Will I have sedation, or can I go back to work afterward?

• Do I need to adjust my blood thinners or diabetes medicines?

• When will I get results and what happens next?

Source and review

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.

Frequently Asked Questions

What is Flexible Sigmoidoscopy?

Why is Flexible Sigmoidoscopy done?

What are the risks of Flexible Sigmoidoscopy?

Bloating, gas and cramping for a short time (common); Minor bleeding, especially after a biopsy or polyp removal (usually stops by itself); Rarely, a tear (perforation) in the bowel wall that may need hospital treatment or surgery; Rarely, a reaction to sedation, if used; Go to the emergency department promptly if, after the test, you have severe or increasing belly pain, a swollen hard belly, fever or chills, heavy bleeding or clots, black stools, dizziness or fainting.

How do I prepare for Flexible Sigmoidoscopy?

Your team will give written instructions. Most people use an enema (a small liquid given into the rectum) once or twice shortly before the test to empty the lower bowel; sometimes a laxative is used instead; Tell the team about all your medicines, especially blood thinners (warfarin, apixaban, rivaroxaban, clopidogrel, aspirin) and diabetes medicines, and do not stop them unless you are told to; Tell the team about allergies, pregnancy, heart or lung conditions, or previous bowel surgery; You can usually eat lightly and drink as normal unless told otherwise. Follow your unit’s instructions on food and drink; Many people have it without sedation. If sedation is planned, arrange for an adult to take you home.