Colonoscopy

During a colonoscopy, a thin, flexible tube with a tiny camera on the end is gently guided through your back passage to look at the entire lining of your large bowel. You will be sedated (given medication to make you drowsy and comfortable), so you will not be aware of most of the procedure. It usually takes between 20 and 45 minutes. If anything needs attention — such as a polyp (a small growth on the bowel wall) — it can usually be removed or sampled at the same time, so a second procedure is rarely needed.

Your GP or specialist may recommend a colonoscopy if you have any of the following:

• Bowel cancer screening — whether you are at average risk (e.g. you are over 45) or higher risk because of a family history of bowel cancer or polyps, or because a home stool test (FOBT — faecal occult blood test) came back positive
• Rectal bleeding (blood on or in your stool) or iron deficiency anaemia (low iron levels that are not explained by your diet)
• A change in your bowel habits — such as looser stools, constipation, or altered frequency — lasting more than four to six weeks
• Follow-up after previous polyps or bowel cancer, to make sure nothing new has developed
• Assessment or monitoring of inflammatory bowel disease (IBD), such as Crohn's disease or ulcerative colitis
• Unexplained abdominal symptoms, such as pain or bloating, that have not resolved with other investigations

• Gives a clear, direct view of the entire large bowel lining
• Any polyps (small growths) found can be removed on the spot, and tissue samples can be taken for analysis — all in the same appointment
• Most people go home the same day and are back to normal activities the next morning
• The standard test for detecting bowel polyps — and unlike CT-based screening, can both diagnose and treat in the same session

Serious complications from colonoscopy are uncommon, but it is important that you understand what they are so you can make an informed decision. These are discussed with you before your procedure.

• Perforation (a small tear in the bowel wall) — this is rare, occurring in roughly 1 in every 1,000 colonoscopies. The risk is slightly higher if a polyp is removed at the same time. If it does happen, it is usually identified and managed promptly, and may require further treatment.
• Bleeding after polyp removal — a small amount of bleeding occurs in around 1 to 2 in every 100 polypectomies (polyp removal procedures). In most cases this can be treated during the same procedure or settles on its own. Heavy or ongoing bleeding is uncommon.
• Missed lesions — no camera examination is perfect. Very small polyps (under a few millimetres) may occasionally be missed; in published series the miss rate for very small polyps is around 5–15%. This is why follow-up colonoscopies are scheduled if you are in a higher-risk group.
• Sedation effects — serious reactions to sedation are rare. You may feel drowsy or a little groggy for several hours afterwards, which is why you need someone to drive you home.
• Bloating and cramping afterwards — this is very common and is caused by the air used to inflate the bowel during the procedure. It usually settles within a few hours.
• Incomplete procedure — on rare occasions it is not possible to reach the full length of the bowel in a single examination. In published series this is uncommon. If it does occur, a CT colonography (a scan of the bowel) will be arranged to complete the assessment.

Good preparation matters: a properly prepared bowel gives the clearest view and the safest, most thorough examination. There are three elements to it — a low-residue diet for a few days beforehand, a bowel preparation drink the day before (and on the morning of your procedure), and standard fasting in the hours immediately before admission. Because you will be sedated, you also need a responsible adult to drive you home.

Your specific instructions — including the right preparation for you, the hour-by-hour timing, and any medication adjustments — are kept in dedicated, regularly updated guides. Please use these rather than relying on memory:

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 guides above.

• Make sure you have arranged for a responsible adult to drive you home — because of the sedation, you cannot drive or operate machinery for the rest of the day, even if you feel fine
• When you arrive at the endoscopy unit, you will check in at reception and a nurse will go through a short assessment with you, check your details, and answer any last-minute questions
• A small cannula (thin plastic tube) is inserted into a vein in your arm, and sedation is given by an anaesthetist. Most people have no memory of the procedure at all
• The colonoscope (a thin, flexible camera tube) is gently guided through your back passage, and the full length of your large bowel is carefully examined
• If any polyps are found, they are removed at the same time — you will not feel this
• The whole procedure usually takes between 20 and 45 minutes. You will then rest in the day-stay recovery area for one to two hours while the sedation wears off
• Before you leave, you will be talked through what was found by Mr Nguyen or another member of the team, and given a written copy of the endoscopy report to take home
• If any tissue samples (biopsies) or removed polyps are sent to the laboratory, results are usually back within two to six weeks and are discussed at a follow-up review — usually a telehealth (phone or video) appointment at no charge for endoscopy patients. If anything concerning is found, the review is brought forward and held in person. You are always welcome to request an in-person appointment if you would prefer one

• On the day: Rest at home. The sedation can leave you feeling drowsy for several hours — this is normal and will pass. Do not drive, operate machinery, drink alcohol, or sign legal documents for 24 hours after sedation.
• The next day: You can eat normally and return to your usual activities. Some bloating or mild cramping for a few hours after the procedure is very common — caused by the gas used during the examination — and settles quickly.
• If a polyp was removed: no restrictions on activity. A very small amount of blood in the stool over the following few days is not a cause for concern. Heavy or persistent bleeding warrants prompt contact — see the warning panel below.
• Next colonoscopy: depends on what was found. You will be given a personalised surveillance recommendation before you leave — typically 5–10 years, depending on the polyps found, and longer if the examination was clear.
• Follow-up review: arranged within 2–6 weeks. For endoscopy patients this is usually a telehealth appointment at no charge. An in-person review (e.g. if further treatment is needed) 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.

Concerns after your procedure: If something doesn't feel right, please call our rooms on (03) 9816 3951 and leave a message — it will be sent directly to Mr Nguyen as a text. You can also text the office mobile on 0499 090 126. We aim to get back to you promptly during business hours.

Emergencies: If you are experiencing a life-threatening emergency — such as severe pain, heavy bleeding, or difficulty breathing — call 000 immediately or go straight to your nearest emergency department. Do not wait for a call back from our rooms. The Austin Hospital Emergency Department can be reached on (03) 9496 5000.