Colonoscopy
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Learn what to expect when visiting the Emergency Department. Learn More
Overview
A colonoscopy is a procedure that lets a gastroenterologist examine the entire large intestine (colon) and the last part of the small intestine. A flexible scope with a camera is passed through the rectum upwards into the colon, under sedation. Colonoscopy is the gold standard for diagnosing bowel diseases and for screening for bowel cancer. Polyps — small growths that can turn into cancer over years — can be detected and removed in the same procedure, making colonoscopy both diagnostic and preventive.
What is this test?
A thin, flexible scope with a high-definition camera is gently advanced from the rectum through the entire length of the colon (about 1.5 metres) to its junction with the small intestine. The doctor examines the colon lining as the scope is slowly withdrawn — this is when most findings are made. Polyps can be removed (polypectomy) and biopsies taken during the same procedure.
Why your doctor may order it
- Bleeding from the rectum or in the stools
- Change in bowel habits — new constipation, new diarrhoea, change in stool calibre
- Unexplained iron-deficiency anaemia (looking for slow blood loss)
- Persistent abdominal pain with bowel symptoms
- Screening for colorectal cancer — typically from age 45 to 50, earlier with family history
- Surveillance after previous polyp removal
- Investigating inflammatory bowel disease (Crohn's, ulcerative colitis)
How long does it take?
The colonoscopy procedure takes 20 to 45 minutes, depending on the anatomy and whether polyps are removed. With sedation recovery and observation, plan for 3 to 4 hours at the hospital. The full preparation — clear liquid diet and bowel cleansing — starts the day before, so the total commitment is about 24 to 36 hours.
How to prepare
- Bowel preparation is the most important part — and the most demanding. The colon must be completely empty for the procedure to be useful.
- Two to three days before: avoid seeds, nuts, popcorn, whole grains, and red meat.
- One day before: switch to clear liquids only — water, clear soup, clear juices, black tea/coffee without milk. No solid food, no milk, no red or purple drinks.
- Evening before and morning of: take the bowel cleansing solution (PEG-based) exactly as prescribed. The volume is large; sip steadily over the recommended time.
- You will pass watery stools many times — this is the prep working. Stay near a toilet.
- Fast completely for 4 to 6 hours before the procedure (your team will give exact timings).
- Tell us about all medications, especially blood thinners, iron tablets, and diabetes medicine. Iron in particular must be stopped 5 to 7 days before.
- Arrange someone to accompany you — you cannot drive for 24 hours after sedation.
What to expect during the test
You change into a hospital gown and a cannula is placed. Sedation is given through the cannula and you become drowsy within a minute. You lie on your left side. The scope is gently inserted through the rectum and advanced through the colon. Small amounts of air or carbon dioxide are pumped in to open the bowel for clear viewing. Most people remember little or nothing. The procedure is generally well-tolerated under sedation. Polyps, if seen, are usually removed during the same procedure. Biopsies are taken if needed. The scope is then withdrawn carefully while the doctor takes a final detailed look.
After the test
- You rest in recovery for 30 to 60 minutes while the sedation wears off.
- Some bloating and gas pains are common for a few hours afterwards — passing wind relieves them.
- Start with light food once you feel ready. Most people are back to a normal diet by the next day.
- Do not drive, operate machinery, sign legal documents, or drink alcohol for 24 hours.
- If polyps were removed, avoid heavy lifting and strenuous activity for 2 to 3 days.
- Watch for warning signs and contact us immediately if you have: severe or worsening abdominal pain, heavy bleeding from the rectum, fever, or breathing difficulty.
- The colonoscopy report is given the same day. Biopsy and polyp histopathology results take 3 to 7 working days.
Do's and Don'ts
- Follow the bowel preparation instructions exactly — a poor prep means a poor procedure or a repeat one.
- Drink plenty of clear liquids during the prep to stay hydrated.
- Stop iron supplements 5 to 7 days before.
- Arrange someone to take you home.
- Rest for 24 hours after the procedure.
- Don't eat solid food on the day before the procedure.
- Don't drink red or purple liquids during the prep — they can look like blood in the colon.
- Don't continue blood thinners unless your doctor has confirmed it is safe.
- Don't drive or make important decisions for 24 hours after sedation.
- Don't ignore severe pain, heavy bleeding, or fever after the procedure — call us straight away.
Understanding your results
The report describes the appearance of the colon lining and lists any polyps removed or biopsies taken. “Normal study” means no significant abnormality was found — and is reassuring. If polyps were found, they will have been sent for histopathology. Most polyps are benign, but the type and size affect when your next colonoscopy will be needed. The histopathology report and your gastroenterologist together decide on follow-up.
Frequently asked questions
The prep is the hardest part for most people — but it is essential. A poorly prepared bowel means the doctor cannot see the lining properly. There is no useful alternative for screening of comparable accuracy.
With sedation, most people remember little of the procedure. Some bloating and gas pains for a few hours afterwards are normal.
Yes. Serious complications (perforation, significant bleeding) are rare, especially in experienced hands. We will discuss the specific risks with you before the procedure.
For screening in an average-risk person, every 10 years from age 45 to 50. With polyps, family history, or inflammatory bowel disease, the interval is shorter — your doctor will recommend the right gap for you.
Some patients do, particularly if they need to drive afterwards. Most find it significantly more uncomfortable. The choice is yours, but we usually recommend sedation.