Flexible sigmoidoscopy

A flexible sigmoidoscopy uses the same thin, flexible camera tube used in a full colonoscopy — but instead of travelling all the way around your large bowel, the camera is guided only through the lower portion. That means the rectum (the very end of your bowel), the sigmoid colon (the S-shaped section sitting just above the rectum), and the descending colon (the left side of your large bowel) can all be examined carefully. These are the areas most likely to explain symptoms like rectal bleeding, mucus, or discomfort around the back passage.

Because only part of the bowel is examined, you do not need the full bowel-cleansing preparation that comes with a colonoscopy — no large volumes of liquid to drink the night before. Instead, a simple phosphate enema (a small amount of fluid gently given into your back passage to empty just the lower bowel) is done by the nursing staff on the day. You will be given sedation so you are comfortable and relaxed throughout, and from start to finish the whole thing takes around 10–15 minutes. It is a short procedure, but it gives clear, detailed information about exactly what is going on in your lower bowel.

A flexible sigmoidoscopy may be recommended if any of the following sound familiar:

• You have noticed rectal bleeding (blood on the toilet paper or in the bowl) and the most likely cause is somewhere in the lower bowel
• You have been told you may have proctitis or distal colitis — that is, inflammation of the lining of your rectum or the lower part of your colon — and a direct look is needed to assess how it is responding to treatment
• You have had bowel surgery and need ongoing check-ups — for example, to look at the join (called an anastomosis) that was made inside your rectum and make sure it has healed well
• You had a rectal polyp (a small growth on the bowel lining) removed in the past and it is time for a follow-up check to make sure nothing new has appeared
• You are experiencing symptoms around your back passage — discharge, pressure, discomfort, or mucus — that need to be properly assessed
• A focused look at the lower bowel is the right first step, and a decision can be made from there about whether a full colonoscopy (which looks at the entire large bowel) is also warranted

• Simpler preparation than you might expect — a short enema given by the nursing staff on the day is all you need. No large bowel-cleansing drinks, no fasting from the evening before, no disrupted day prior to the procedure
• You will be comfortable throughout — sedation is given through a small drip in your hand before the procedure begins, so you are relaxed and drowsy during the examination. Most people have little or no memory of it afterwards
• It is quick — the camera examination itself typically takes 10–15 minutes. You will then rest in the day-stay unit while the sedation wears off, and you are usually ready to go home within 30–60 minutes of waking up
• The risks are very low — lower than with a full colonoscopy, because only the lower portion of the bowel is examined. Serious complications are uncommon
• Problems can often be addressed in the same sitting — if something that needs attention is seen, such as a small polyp (a growth on the bowel lining) or an area of inflammation, a biopsy (a tiny tissue sample sent to the laboratory) or a polypectomy (removal of a small polyp) can be performed during the same procedure, without needing to bring you back
• It gives clear, accurate answers — a direct look at the lining of your rectum and lower colon gives precise information about what is causing your symptoms, rather than relying on indirect tests

Serious complications from a flexible sigmoidoscopy are uncommon — this is considered one of the safest endoscopic procedures. That said, it is worth understanding what can occasionally happen, so you can make an informed decision and know what to look out for afterwards.

• Perforation (a small tear in the bowel wall) — this is rare, occurring in published series in roughly 1 in every 3,000 to 1 in every 10,000 flexible sigmoidoscopies. If it did happen, it would be identified quickly and treated promptly. To put it in perspective: the risk is lower than for a full colonoscopy, because only the lower bowel is examined.
• Bleeding after a biopsy or small polyp removal — if a small tissue sample (biopsy) was taken or a small polyp removed, there is a small chance of some minor bleeding. In most cases this settles on its own without any treatment needed. The risk is less than 1 in 100. Larger polyp removal carries a slightly higher bleeding risk — see the colonoscopy page for details.
• The upper bowel is not examined — a flexible sigmoidoscopy only looks at the lower portion of your large bowel. If your symptoms could be coming from higher up, or if something is found that warrants a fuller look, a complete colonoscopy may be recommended as a next step. This is not a failure — it is simply gathering more information if it is needed.
• Wind discomfort and bloating — a small amount of air is gently introduced into the bowel during the examination to open it up and give a clear view. It is very common to feel some cramping, bloating, or an urge to pass wind for an hour or two afterwards. This is harmless and settles on its own; a gentle walk around can help it pass more quickly.

Before your procedure, your individual situation will be discussed with you — what is expected, what is being looked for, and what you should know beforehand. Please bring any questions you have to that conversation. There is no such thing as a silly question when it comes to understanding your own care.

Preparation for a flexible sigmoidoscopy is simpler than for a full colonoscopy. There is no large volume of laxative to drink, and no disrupted day the day before. The lower bowel is cleared with a phosphate enema — a small amount of liquid gently given into the back passage — by the nursing staff at the endoscopy unit, 1–2 hours before your procedure. You do not need to do anything special at home the evening before.

You will still need to fast for sedation, and any regular medications may need adjustment. The full fasting and medication instructions are in the dedicated guide below. You will also need a responsible adult to drive you home and stay with you for a few hours afterwards — this is a firm safety requirement, not a suggestion, even if you feel fine when you wake up. Wear loose, comfortable clothing on the day.

If you take blood thinners, diabetes medication, GLP-1 weight-loss injectables, or iron supplements, please flag this when you book — these need specific adjustments before the procedure. Full details are in the guide above.

It helps to know exactly what is going to happen, so here it is, step by step:

• When you arrive at the endoscopy unit, the nursing team will welcome you, check you in, and explain what is about to happen. They will then administer the phosphate enema — it is quick and the staff do it every single day. You are in calm, experienced hands from the moment you walk in.
• Once you are ready, the sedation (given through a small drip in your hand or arm) will make you feel drowsy and relaxed within a minute or two. Most people are surprised by how gentle this part feels.
• You will be asked to lie on your left side on the procedure table. The thin, flexible camera is then gently guided through your back passage and slowly advanced through your rectum and into the left side of your colon, with the lining inspected carefully along the way.
• If something that needs closer attention is seen — such as an inflamed area or a small polyp (a tiny growth on the bowel lining) — a biopsy (a tiny tissue sample, sent to the laboratory for analysis) may be taken. Under sedation, you will not feel this at all.
• The examination itself takes around 10–15 minutes. When it is done, what was seen is talked through with you in the day-stay area. You will also be given a written endoscopy report to take home, and a copy goes directly to your referring doctor.
• You will then rest comfortably in the day-stay unit for 30–60 minutes while the sedation fully wears off, and once the nursing team is satisfied that you are alert and well, you are free to go home.

• The day of the procedure: Once the sedation has worn off and the nursing team is happy you are alert and steady, you can head home — usually within 30–60 minutes of waking up. You can eat and drink normally from that point. Most people feel perfectly well within a few hours.
• Bloating and wind: It is very common to feel some bloating or an urge to pass wind for an hour or two after the procedure — this comes from the small amount of air used during the examination to open up the bowel for a clear view. It settles on its own, and a gentle walk around the house can help it move along more quickly.
• If a biopsy was taken: You do not need to change your diet or restrict your activities. Simply carry on as normal. The biopsy results take a couple of weeks to come back from the laboratory.
• Your biopsy results: If tissue samples were taken, the histology report (a pathologist's examination under a microscope) is typically ready within 1–2 weeks. Results are discussed with you within 2–6 weeks of your procedure. For most endoscopy patients this is done by phone or telehealth at no charge. If the results need a more detailed conversation, or further management is needed, you will be asked to come into the rooms — and the practice team will reach out to you promptly if anything needs earlier attention.
• Next steps: Depending on what is found, a full colonoscopy may also be recommended. If so, the reasons will be explained clearly — it is not a cause for alarm, just a more complete picture.
• Your follow-up review: A review is routinely arranged within 2–6 weeks of your procedure. For endoscopy patients this is typically a phone or telehealth call at no charge. An in-person review (e.g. to plan further treatment) attracts a standard consultation fee.

For full post-procedure information, including red-flag symptoms to watch for in the days afterwards, see the After Endoscopy aftercare guide.

Worried about something after your procedure? Please call our rooms on (03) 9816 3951 and leave a message — it is sent straight through to Mr Nguyen as a text. You can also text the office mobile directly on 0499 090 126. We aim to get back to you promptly during business hours.

If you are unwell or something feels urgent: Do not wait for a call back from our rooms. Call 000 immediately or go straight to your nearest emergency department. For the Austin Hospital Emergency Department: (03) 9496 5000.