Quick answer. A colonoscopy is a camera examination of the large bowel. A thin, flexible tube with a tiny camera is gently passed through the back passage so a specialist can look closely at the lining of your colon and rectum. It is usually done with sedation for comfort, and polyps can be removed or biopsies taken during the same test. In Singapore it is carried out by a gastroenterologist or colorectal surgeon, and it is one of the safest and most thorough ways to check the bowel.
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Being told you need a colonoscopy can feel daunting, but it is a common, well-established procedure done every day in hospitals and endoscopy centres across Singapore. Knowing what to expect – from the bowel preparation the day before to how results are shared afterwards – can make the whole experience far less worrying. This guide explains each step in plain terms.
What it is
A colonoscopy is a test where a thin, flexible tube with a camera on the end (a colonoscope) is passed through the back passage to look at the lining of the large bowel – that is, the colon and the rectum. The camera sends a clear, magnified picture to a screen, letting the doctor examine the bowel wall in detail. It is regarded as the most thorough way to check the large bowel because the doctor sees the lining directly. Importantly, it is not only a diagnostic test: many findings can also be treated during the same procedure.
Why it’s done
A colonoscopy may be recommended for several reasons. It is used to investigate symptoms such as bleeding from the back passage, a persistent change in bowel habit, unexplained tummy pain, or ongoing changes in weight or blood counts. It is also a key test for bowel (colorectal) cancer screening, including follow-up after a positive stool test. During the procedure, growths called polyps can be removed before they have any chance to become a problem, and the test is used to monitor longer-term conditions such as inflammatory bowel disease.
What it can do that other tests can’t
Other tests can point towards a problem, but a colonoscopy can act on what it finds. Unlike a stool test (such as the FIT test) or a virtual colonoscopy, which can only suggest that something needs a closer look, a colonoscopy lets the doctor remove polyps and take small tissue samples (biopsies) there and then. This means a single test can both find and treat many findings, often sparing you a separate procedure later.
How to prepare
Good preparation is what makes the test reliable, because the bowel needs to be completely empty so the camera can see clearly. Your care team will give you a bowel-cleansing preparation to drink, along with instructions to change your diet in the days beforehand – usually moving to low-fibre foods and then clear fluids. You will also be told when to stop eating and drinking so you are fasting for the procedure.
- Follow the bowel-preparation and diet instructions closely – the cleaner the bowel, the more accurate the test.
- Tell your doctor about all your medicines, especially blood thinners, which may need to be paused or adjusted.
- Ask about your diabetes medicines, as doses may change while you are fasting.
- If you are having sedation, arrange for someone to accompany you home afterwards.
What happens during the procedure
On the day, you will change into a gown and a small tube may be placed in your arm to give sedation, which helps you stay relaxed and comfortable – most people remember little or nothing of the test. You will lie on your side, and the doctor gently passes the colonoscope through the back passage and around the bowel. A little air or gas is used to open up the bowel so the lining can be seen clearly, which can feel like wind or mild pressure. If polyps are found they can be removed, and biopsies can be taken – both painless, as the bowel lining has no pain sensation. The examination itself usually takes only a short time.
After the procedure
Afterwards you will rest in a recovery area while the sedation wears off. It is normal to feel a little bloated or to pass wind for a while as the air used during the test clears – this settles on its own. Because sedation can slow your reactions, you should not drive, operate machinery, sign important documents or make major decisions for the rest of the day. The doctor will often share initial findings with you before you leave, while results from any biopsies take a little longer and are usually explained at a follow-up appointment.
Risks
A colonoscopy is generally very safe, and serious problems are uncommon. It is still important to know the risks honestly. Occasionally there can be some bleeding, particularly if a polyp has been removed, and very rarely a small tear in the bowel wall (a perforation) can occur. There can also be effects from the sedation, such as feeling drowsy or lightheaded. Your care team takes careful steps to reduce these risks and will watch you closely during and after the test, and most people go home the same day feeling well.
Results and next steps
There are a few common outcomes. A normal result means nothing of concern was seen, and your doctor will advise when, if ever, a repeat is needed. If polyps were found and removed, this is a positive step, and the timing of any future check depends on what the polyps were like. Sometimes findings need further care, such as more tests, a referral or treatment, and your specialist will guide you through what happens next. Any recommendation for a repeat colonoscopy is tailored to you, based on what was found and your personal risk.
When to seek urgent help
Recovery is usually smooth, but you should seek urgent care – go to A&E or call 995 – if after your colonoscopy you develop severe or spreading tummy pain, a hard or swollen abdomen, heavy or persistent bleeding from the back passage, fever, breathlessness, or feeling faint. These can be signs of bleeding or a bowel tear and need to be checked without delay.
Common questions
Is a colonoscopy painful?
Most people are given sedation and feel little or no discomfort, often remembering very little of the test. You may notice some wind or mild pressure from the air used, but the bowel lining itself has no pain sensation, so removing polyps or taking biopsies does not hurt.
Is the bowel preparation the worst part?
Many people find the preparation the least pleasant part, as it means drinking the cleansing solution and making frequent trips to the toilet. It is temporary and important – a clean bowel is what allows the doctor to see clearly and give you an accurate result.
Will I be awake during the test?
Sedation is usually offered to keep you relaxed and comfortable. You are not under a full general anaesthetic, but many people are drowsy enough that they recall little of the procedure. Because of the sedation, you will need someone to accompany you home.
How soon will I get my results?
Your doctor can often tell you what was seen soon after the test, once the sedation has worn off enough for you to take in the information. Results from any biopsies take longer to come back from the laboratory and are usually explained at a follow-up visit.
When can I eat and return to normal activities?
You can usually eat soon after the test unless your team advises otherwise, starting with something light. Most people feel back to normal by the next day, though you should avoid driving and important decisions for the rest of the day you are sedated.
Related guides
Sources
- Singapore General Hospital
- HealthHub
- Singapore Cancer Society
- NHS