What is a colonoscopy?
A colonoscopy is an examination of the large bowel — the colon and rectum — using a thin, flexible tube called a colonoscope. The scope is roughly the diameter of a finger. It has a tiny camera and light at the tip, and the images are shown on a screen so your specialist can inspect the entire lining of the large bowel as they go.
In Australia, colonoscopy is the standard investigation for bowel cancer screening, for checking symptoms like rectal bleeding or a change in bowel habit, for monitoring after polyp removal, and for diagnosing conditions like inflammatory bowel disease. Mr Ba Nguyen performs colonoscopies at accredited endoscopy facilities in the Heidelberg area.
How long does it take?
The procedure itself usually takes between 20 and 45 minutes, though it can be longer if the bowel is a more complex shape or if polyps are removed. When you count in arrival, preparation, the procedure, and recovery time, plan for your whole visit to take around three to four hours. You will need someone to drive you home afterwards — you are not allowed to drive, operate machinery, or make any legally binding decisions for 24 hours after receiving sedation.
Step-by-step: what happens on the day
Arrival and check-in. When you arrive, a nurse will greet you, confirm your identity, check your consent form, review your medical history, and go through any allergies or regular medications. They'll particularly ask about blood-thinning medications like warfarin, rivaroxaban, or aspirin, which may have needed to be paused beforehand.
Changing and preparation. You'll change into a hospital gown. A nurse will insert a small drip (intravenous cannula — a thin plastic tube into a vein, usually on the back of your hand or forearm). This is used to give you the sedation and any other medications needed during the procedure.
Meeting your team. Before you're taken to the procedure room, Mr Nguyen and the anaesthetist or sedation nurse will come to see you. This is your chance to ask any last questions, confirm the plan, and have your prep checked. If your bowel preparation wasn't adequate, the procedure may need to be rescheduled — this is why following the prep instructions carefully really matters.
Sedation. Once in the procedure room, you'll lie on your left side on a padded table. The sedation is given through your drip. Most colonoscopies in Australia use propofol (a short-acting sedation medication that puts you into a deep, sleep-like state) either alone or combined with midazolam and fentanyl (a lighter sedation approach). With propofol, you'll have no awareness or memory of anything. With the lighter option, you'll be very relaxed and drowsy. Your oxygen levels, heart rate, and blood pressure are monitored continuously throughout.
Scope insertion and advancement. The lubricated colonoscope is gently inserted through the anus and carefully advanced through the rectum and the rest of the colon. Small amounts of gas (air or carbon dioxide) are put in to open up the bowel wall so the camera can see clearly. Carbon dioxide is absorbed quickly by the body and causes much less bloating afterwards than air does.
Inspection of the bowel lining. Once the scope reaches the caecum — the very start of the large bowel, near where your appendix is — the specialist slowly and carefully withdraws it, inspecting every centimetre of the lining on the way back out. The withdrawal is actually the most important part of the whole procedure: this is when polyps and other changes are found. Current guidelines recommend a minimum withdrawal time of six minutes to ensure nothing is missed.
Polyp removal (if applicable). If a polyp (a small growth) is found, it can usually be removed on the spot — this is called a polypectomy. Small polyps are typically removed using a cold snare — a wire loop that cuts the polyp without heat. Larger polyps may be removed using a hot snare, which uses a gentle electrical current to cut and seal the base at the same time. Any tissue removed is sent to the pathology lab for examination under a microscope.
Completion and scope removal. Once the full inspection is done and any polyps have been dealt with, the scope is gently removed. That's the procedure complete — for a routine colonoscopy, this is typically under 30 minutes.
Recovery. You'll be taken to the recovery area, where nurses will keep an eye on you while the sedation wears off. Most people feel quite comfortable within 30 to 60 minutes. You may feel bloated or pass wind as the gas from the procedure escapes — this is completely normal and usually settles quickly. Before you go home, Mr Nguyen will come and speak with you (and whoever is with you) about what was found, show you any photos taken during the procedure, and explain what happens next.
Sedation: will I be awake?
This is one of the most common things people want to know. The honest answer is: it depends on the type of sedation used, but for most people, you won't be aware of anything at all.
Propofol sedation puts you into a deep, sleep-like state very quickly. You won't be aware of the procedure happening and won't remember any of it. Propofol wears off rapidly too, which is why the recovery is usually quite quick.
Conscious sedation — a combination of midazolam (a relaxation medication) and fentanyl (a pain reliever) — produces a relaxed, drowsy state. Some people remain partially aware but feel no pain; others drift off completely. Midazolam also has a memory-blunting effect, so even people who were technically awake during the procedure often have no recollection of it afterwards.
Which type of sedation you receive will be discussed with you beforehand. In most Australian private facilities, propofol given by an anaesthetist is the standard. The main takeaway is that the overwhelming majority of patients report no awareness and no discomfort at all.
Most people are genuinely surprised by how easy the whole thing is. If there's one thing almost everyone agrees on, it's that the bowel preparation the day before is the hardest part — not the procedure itself.
What can be done during a colonoscopy?
A colonoscopy is more than just a look — it can also treat things at the same time. During the procedure, your specialist can:
- Remove polyps (polypectomy) before they have any chance to develop into cancer
- Take small tissue samples (biopsies) to be examined in a pathology lab
- Treat areas of active bleeding using small clips or cauterisation (heat sealing)
- Gently stretch areas of narrowing — called strictures — in the bowel
- Remove foreign bodies in certain situations
- Place a small ink tattoo on the bowel wall to mark the location of something for future surgery
This ability to both look and treat in one session — under the same sedation — is one of the big advantages colonoscopy has over other bowel-imaging tests like CT colonography.
Are there any risks?
Colonoscopy is a very safe procedure, but like any medical procedure it carries a small risk of complications. It's important to be aware of these, even though serious problems are uncommon:
- Bleeding: The most common complication, and most often occurs after a polypectomy. It affects roughly 1 in 200 to 1 in 500 procedures. Minor bleeding usually settles without treatment; significant bleeding is uncommon but does happen occasionally.
- Perforation: A small tear in the bowel wall — this occurs in approximately 1 in 1,000 diagnostic colonoscopies. The risk is slightly higher if polypectomy is performed. A perforation usually requires hospitalisation and sometimes surgery to repair.
- Sedation risks: Effects on the heart or breathing from sedation are rare, but can occur — particularly in people with significant heart or lung conditions. Your medical history is carefully reviewed before any sedation is given.
- Missed lesions: No test is perfect. The chance of missing a polyp larger than 10 mm is low (around 2–5%), but smaller polyps can occasionally be missed. This is one of the reasons follow-up surveillance colonoscopies are recommended at set intervals.
Seek urgent medical attention after your colonoscopy if you develop severe abdominal pain, heavy rectal bleeding (soaking through a pad or passing clots), a fever above 38°C, or vomiting that won't settle. These symptoms are uncommon, but they can signal a complication that needs prompt assessment.
After the procedure: what to expect
Once the sedation has worn off, most people feel reasonably comfortable. Here's what's normal in the first few hours:
- Mild bloating or cramping — this is from the gas used during the procedure and usually settles within a couple of hours
- A small amount of blood or mucus in your first bowel motion — this is expected, especially if a biopsy or polypectomy was done
- Tiredness from the sedation — most people feel entirely back to themselves by the next morning
You can eat and drink normally once you're fully awake and have been discharged. Start with something light and build up as you feel ready. If a polypectomy was performed, Mr Nguyen will give you specific instructions about what to eat and what to avoid for a few days.
If tissue samples (biopsies) or polyps were removed, the pathology results are usually available within one to two weeks. Mr Nguyen's rooms will contact you to talk through the results and arrange any follow-up needed.
Frequently asked questions
With propofol sedation, which is the most common approach in Australian private facilities, you'll be in a deep, sleep-like state and have no awareness or memory of the procedure. With conscious sedation (midazolam and fentanyl), you'll feel very relaxed and may not remember anything either — even if you were technically partially aware at the time.
The scope is gently advanced to the caecum (the start of the large bowel) and then slowly withdrawn — the whole process typically takes 20 to 45 minutes. The withdrawal phase — when the careful inspection happens — is not rushed. In fact, taking enough time on the way out is one of the most important quality markers for a thorough colonoscopy.
No — this is a firm rule. You cannot drive, operate machinery, or make any legal decisions for 24 hours after receiving sedation. You'll need someone to drive you home. A taxi or rideshare is acceptable if you don't have a friend or family member available, but you should not be on your own for the first few hours at home if possible.
Yes. Before you leave, Mr Nguyen will come and speak with you in the recovery area to explain what was found. If polyps were removed, they'll be sent to the pathology lab and results usually take one to two weeks. Mr Nguyen's rooms will contact you once the results are back to discuss what they mean and what, if anything, needs to happen next.
Most people feel well enough to go back to work the following day. If your work involves heavy lifting or strenuous activity, you may need an extra day or two — particularly if a polypectomy was done. Mr Nguyen will guide you based on what was found and done during your procedure.
No — they examine different parts of the digestive tract. A gastroscopy looks at the upper end (oesophagus, stomach and duodenum) using a scope passed through the mouth. A colonoscopy looks at the lower end (large bowel) via the anus. Some patients have both procedures done at the same visit, under the same sedation.
The bottom line
A colonoscopy is a safe, well-tolerated procedure that can find — and in many cases prevent — bowel cancer by removing pre-cancerous polyps before they have any chance to progress. With modern sedation and an experienced specialist, most people have no memory of the procedure at all and are back to feeling like themselves within a few hours. By almost universal agreement, the preparation the day before is the hardest part.
If you've been referred for a colonoscopy, or you'd like to talk about whether one is right for you, Mr Ba Nguyen's rooms are happy to guide you through the whole process.
Learn more about this procedure — including what to expect, benefits, risks, and recovery.
Procedure details →Want to talk through what to expect?
Call Mr Nguyen's rooms on (03) 9816 3951, ask your GP for a referral, or send us an enquiry →