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.
A sigmoidoscopy uses an endoscope to look at the lining of the lower part of your large bowel. This helps us to diagnose any symptoms you have, or check your existing bowel condition.
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.
We may use a small instrument, called a proctoscope, to check and treat piles (haemorrhoids) if necessary.
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
Preparing for a flexible sigmoidoscopy
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.
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.
Wear loose-fitting clothes on the day of the test.
Having an enema
To make sure the doctor has a clear view of your large bowel with the camera, you will need to have an enema before your procedure.
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.
When you arrive at the endoscopy unit
When you arrive, please give your name to the receptionist. We'll ask you 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.
We'll ask you to remove your jewellery. This is because you should not wear any metal during the procedure if you are having polyps removed. You want to leave any valuable jewellery at home, as we cannot be responsible for any valuables lost while in the unit.
We'll ask you 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.
Our endoscopy teams run up to 5 procedure rooms at the same time. This means that 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 than 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.
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 treatment 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.
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.
Resource number: 0920/VER8
Last reviewed: June 2022
Next review: June 2025