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Flexible sigmoidoscopy


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A flexible sigmoidoscopy is a procedure to look at your large bowel (colon).

It uses a thin, flexible tube called an endoscope. This is about the thickness of your little finger, with a camera and light at one end.

It is passed through your bottom (anus) and carefully moved around your large bowel by a specially trained doctor or nurse, called an endoscopist.

By looking down the endoscope, your endoscopist can get a clear view of the lining of your large bowel.  

Information on this page

What is a sigmoidoscopy?

A sigmoidoscopy uses an endoscope to look at the lower part of your large bowel, which is called the sigmoid colon.

It looks at the lining of the sigmoid colon, to help diagnose any symptoms you have, or check any existing bowel condition you might have. 

During a sigmoidoscopy, small tissue samples (biopsies) of your bowel might be taken. These can be tested under a microscope to help with your diagnosis.

Small growth in the bowel (polyps) can also be removed during this procedure.

You might have a flexible sigmoidoscopy if you have:

  • bleeding from your bottom
  • pain in your tummy
  • ongoing diarrhoea
  • changes to your bowel habits
  • a strong family history of bowel cancer
  • had an X-ray and more information is needed about the lower end of your bowel
  • an existing condition, such as colitis, that needs reviewing
  • been referred by your GP and booked into the rectal bleed clinic, which involves a flexible sigmoidoscopy as part of the assessment and treatment 

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Risks of a flexible sigmoidoscopy

Serious complications are extremely rare (1 person in every 10,000 who have this procedure).

Your doctor or specialist nurse will talk to you about any risks in more detail. Please ask them about any questions or concerns you have.

The most serious risk is the endoscope damaging your large bowel during the test.

This can cause an infection, bleeding or a small hole or tear (perforation) of the lining of the bowel. If this happens, your tummy might become painful and bloated. You might need medicine or surgery to treat the problem.

If a biopsy is taken, or a polyp is removed during the procedure, you might pass a small amount of blood from your bottom after the test. This should only happen up to 12 to 24 hours after the procedure, and is usually no more than a few teaspoons full.

Sometimes, the procedure might need to be stopped, or might not be finished. This can happen if you find the procedure too uncomfortable, or if the bowel preparation did not empty your bowel fully. If this happens, the procedure might need to be repeated, or you might need to have a different procedure.

Other proedure options

  • CT scan or CT enema scan. This is a special type of X-ray that can give more information than a normal X-ray. However, it cannot be used to take biopsies or remove polyps, so you might still need a sigmoidoscopy.
  • Rigid sigmoidoscopy. This might be done in the outpatient department, but it only looks at the very last section of your bowel. If your doctor or nurse cannot diagnose your symptoms after this procedure, you might still need a flexible sigmoidoscopy which looks slightly further up your bowel.
  • Faecal occult blood test (FOB). This tests for hidden blood in your poo (stool). However, you might still need a flexible sigmoidoscopy if this test is positive.


  • Asking for your consent


    We want to involve you in decisions made about your care and treatment. If you decide to go ahead, you will be asked to sign a consent form to say that you agree to have the procedure, and you understand what it involves.

    If you would like more information about our consent process, please speak to a member of staff caring for you

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Preparing for a flexible sigmoidoscopy

  • It is important that you do not eat any food for 6 hours before your procedure. This is so the doctor has a clear view with the camera. 
  • Do not drink anything for 4 hours before.
  • You can have small sips of water up to 2 hours before.
  • Wear loose-fitting clothes on the day of the test.
  • If you are having sedation, and are going home within 24 hours, you must have someone to take you home and stay with you overnight. They must be over 18 years old. They should come with you for the appointment, or be contactable by phone when you are ready to leave.

If you do not have someone to take you home and stay with you overnight, your procedure might be cancelled.

If you cannot arrange for someone to collect you, please contact the endoscopy unit to discuss alternative arrangements.

Your usual medicines

You should have had a chance to talk to your doctor or nurse about any medicines you are taking.

  • If you are taking medicines to prevent blood clots, please tell your doctor or nurse before the day of your appointment. This is anti-platelet or anticoagulant medicines, such as aspirin, clopidogrel, warfarin, rivaroxiban or dabigatran.
  • You should also tell your doctor or nurse before the day of your appointment if you take sedatives, chronic pain medicine, or medicines for diabetes.

Take all of your usual medicines as normal, unless you have been told not to by your doctor or nurse.

Having an enema

You will be asked to have an enema before you have a flexible sigmoidoscopy.

The enema helps clear your bowel, so the endoscopist can see all of your bowel clearly.

The enema is a small bottle of fluid that you put into your bottom, using a small tube.

Enemas are safe, gentle and surprisingly easy to use. Most people find it convenient and comfortable to use the enema at home.

  • If you use the enema yourself at home, do this before you come for your appointment. Please contact the endoscopy unit to arrange to collect the enema, and instructions on using the enema.
  • The enema can also be given by a nurse once you have had your pre-assessment when you arrive in the endoscopy unit. You do not need to arrive any earlier than the appointment time we have given you.

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How and when to use the enema

Make sure you have read through this information carefully before using the enema.

The enema is a small bottle of fluid that is put in your bottom via a small tube.

  • If you are having the enema at home, it needs to be used 2 hours before you leave home on the day your procedure. 
  • Use the enema even if you have recently had a poo. 
  • You will usually need to go to the toilet within 15 minutes of using it.
  • You must not eat or drink anything after the enema until after your procedure.

When not to use the enema

Do not use the enema if you are having treatment for kidney disease, colitis or have bloody diarrhoea.

If you have any concerns about using an enema, contact the endoscopy unit and speak to a nurse.

Before using the enema

You will need a:

  • jug or bowl of warm tap water
  • towel
  • bed to lie down on

Make sure you are near a toilet. 

Find somewhere comfortable to lie down and have a towel to lie on in case of leakage.

How to use the enema

  1. Put the unopened enema bottle or pack into the jug of warm (not hot) water for about 5 minutes. This will warm the enema to body temperature.
  2. Spread the towel on the bed, where your bottom will be.
  3. Remove the enema bottle or pack from the jug of warm water.
  4. Remove the cap from the nozzle of the enema bottle.
  5. Lie on your left side, on the towel, with your knees up towards your chest.
  6. Put the full length of the nozzle carefully and gently into your bottom, up to the disk at the end of the nozzle.
  7. Squirt in all the contents until empty.
  8. Gently remove the nozzle from your bottom, and stay lying down.
  9. Try to hold the liquid inside your bottom for about 5 to 10 minutes. Do not worry if you cannot hold it that long. To take your mind off the enema, you might find it helpful to read, or watch TV.
  10. When you can no longer hold the enema, and you have the urge to go to the toilet, get up slowly and walk to the toilet.
  11. Make sure you do not get up too quickly to go to the toilet. Some people feel faint or dizzy when they try to get up. If this happens to you, lie back down until the feeling passes
  12. Go to the toilet, but do not worry if you do not poo at first.
  13. Stay near a toilet for the next hour.

Some people might have mild stomach cramps for a short while.

The effects of the enema will then stop. and you should have no problems travelling to the endoscopy unit.

If you do not have any bowel movements within an hour, or if you have any significant bleeding, contact the endoscopy unit for more information. 

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When you arrive at the endoscopy unit

  • On arrival, please give your name to the receptionist.
  • You will be asked to wait in the waiting area until you are seen by an endoscopy nurse.
  • The nurse will ask you about your medical history. Please tell the nurse if you have had any reactions or allergies to other procedures or medicines in the past.
  • You will be asked to take off your jewellery. This is because you should not wear any metal during the procedure if you are having polyps removed.
  • You might wish to leave any valuable jewellery at home, as we cannot be responsible for any valuables lost while in the unit.
  • You will be asked to remove all of your clothing and change into a gown and some disposable underwear.
  • You might want to bring your own dressing gown and slippers with you (we do supply non slip socks).
  • Once you are ready, you will be taken to the second waiting area, signposted ‘sub wait area.’
  • Your endoscopist will explain more about the procedure and answer any questions you have.

Waiting times

Our endoscopy teams run up to 5 procedure rooms at the same time. Therefore, a person who arrived after you might be called in before you.

This does not mean you have been forgotten, but that the other person is on a different list to you.

We also deal with emergencies. These can take priority over your appointment, meaning we might have to ask you to wait. We apologise in advance if this occurs but please be patient with us and check at the reception desk if you are concerned.

We do everything we can to avoid you waiting any longer than necessary. However, because every procedure takes a different length of time, sometimes it is hard to give exact timings.

We will update you on how long you are likely to be with us.

Please be prepared to be with us for the whole morning or afternoon, depending on when your appointment time is. 

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During a sigmoidoscopy

The procedure takes about 15 minutes.

An endoscopy nurse will be with you during the whole procedure to reassure you.

It is usually performed with sedation or an injection of painkillers. You can choose not to have sedation if you prefer.

Sedation is a medicine that makes you relaxed and sometimes sleepy, but does not put you to sleep. Your endoscopist will explain this to you in more detail.

If you are concerned about pain or discomfort, you might want to use gas and air (Entonox). This is commonly used for pain during childbirth. It is also used widely by the ambulance service, and in hospitals for a variety of procedures and conditions.

Read more about having gas and air (entonox) during your procedure.

  1. You will be asked to lie down on your left-hand side on a couch with your knees bent.
  2. The endoscopist will start by putting a finger into your bottom to perform a rectal exam.
  3. This will help lubricate the anal passage, and to check if there are any haemorrhoids or growths in your anal passage.
  4. The endoscope will then be put into your lower bowel through your bottom.
  5. Air will be passed down a channel in the endoscope. This will expand your bowel to make it easier to see during the procedure. 
  6. This might make you feel slightly bloated. You might feel the need to go to the toilet, but you will not be able to as your bowel will be empty.

Many people fart during the test. This is perfectly normal and is nothing to be embarrassed about.

If you have polyps, your endoscopist can remove these. You will not feel this.

When a polyp is particular big or in a difficult position, you might need to wait for another time for it to be removed and re-booked on a special list. 

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  • You might have some cramps and tummy pain during or after the procedure. This is from the air that we use to inflate your bowel during the procedure. 
  • You might also have short periods of discomfort or pain from certain parts of the procedure. This should not last long.
  • Sometimes, the nurse will press gently on your stomach or your position might be changed to help the passage of the endoscope.
  • You will not feel anything if any biopsies are taken. 

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After a sigmoidoscopy

The nurse will take you to the recovery area. They will check your observations regularly, and monitor you for any complications.

They will offer you some tea and biscuits.

  • If you have had sedation, you will need to rest quietly until the sedative has worn off. This usually takes a couple of hours.
  • If you have not had sedation, you will be taken to the discharge area where you will be given a copy of the test results. You can leave the hospital straight after your procedure.

You might still feel a little bloated from the air passed into your bowel during the procedure. This should pass quite quickly.

The results of any biopsies or polyps taken during the procedure will usually be available within 2 weeks.

You and your GP will get a letter with the results and recommendations for your care and treatment.

You might be given an appointment to come back to the clinic. This will be posted out to you.

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When you go home

If you have had sedation or a general anaesthetic and are going home within 24 hours, you must have someone to take you home and stay with you overnight.

If you are going home within 24 hours, you should rest at home.

You should not:

  • drive a car, or ride a bicycle
  • operate machinery, or do anything needing skill or judgement
  • drink alcohol
  • take sleeping tablets
  • go to work
  • make any important decisions, sign contracts or legal documents

You should rest at home after your procedure.

You can eat and drink normally, and should be able to carry out your usual activities 24 hours after the test. 

Important. If you develop any of these symptoms, contact your GP or go to the emergency department (A&E). 

  • Severe tummy (abdominal) pain.
  • High temperature (fever).
  • You pass large amounts of blood.

Take your endoscopy report with you.  

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A specialist nurse will often be able to tell you your results before you leave the hospital.

If you have had a sedative, it is a good idea to have someone with you when the results are being discussed, as you might not remember all of the details due to the sedative.

If you have had biopsies taken the results can take up to 2 weeks.

You and your GP will get a letter with the results and any recommendations for your care and treatment. 

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Follow-up appointment

If your results suggest that you need a follow-up appointment, the Patient Access Team will contact you to arrange this. 

If it is urgent, you will be given an appointment on the day of your procedure. 

You might be told after your procedure that your follow-up is a virtual clinic. This is when the clinical team review your results without you being there.

They will make a decision on next steps for you based on the results. You and your GP will then get a letter from the clinic telling you if you need to return to the hospital, or if you can be discharged back to your GP.

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Ref number: 0920/VER5

Date published: October 2018 | Review date: October 2021

A list of sources is available on request

Where next?

Contact us

If you need to change your appointment, or if you have any questions or concerns about your procedure, please contact the endoscopy unit

Phone 020 7188 8887

Nurse in charge     020 7188 7188  extension 54059

Monday to Saturday, 9am to 5pm. 

In case of emergency outside of these hours, phone 020 7188 7188 and ask to be put through to the on-call gastroenterology registrar.

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