What Is Colonoscopy?
Dr Dennis Koh
Medical Director & Senior Consultant Colorectal Surgeon
MBBS (Nottingham), B Med Sci (Nottingham), MMed (Surgery), FRCS (Edinburgh), FAMS
Dr Sharon Koh
Senior Consultant Colorectal Surgeon
MBBS (Singapore), MMed (Surgery), FRCS (Edinburgh), FAMS
Dr Pauleon Tan
Senior Consultant Colorectal Surgeon
MBBS (Singapore), MMed (Surgery), FRCS (Edinburgh), FAMS
Colorectal cancer is one of the most commonly diagnosed cancers in Singapore. Regular screening can help detect colorectal cancer at an earlier stage and identify precancerous polyps before they develop into cancer.
At Colorectal Practice, colonoscopies are performed by Senior Consultant Colorectal Surgeons Dr Dennis Koh, Dr Sharon Koh, and Dr Pauleon Tan. The team has experience in colorectal cancer screening, advanced endoscopy and the diagnosis and treatment of colorectal conditions.
A colonoscopy examines the entire colon and rectum using a thin, flexible tube with a camera called a colonoscope. During the procedure, the doctor can:
Identify polyps, inflammation or abnormal tissue
Remove polyps where necessary
Take biopsies for further testing
The procedure is usually performed under sedation for patient comfort.
When Is a Colonoscopy Recommended?
A colonoscopy may be recommended for:
Colorectal cancer screening
To detect and remove precancerous polyps or identify colorectal cancer at an early stage.
Investigating symptoms
Such as rectal bleeding, persistent changes in bowel habits, unexplained abdominal pain or weight loss.
Follow-up after an abnormal screening test
Such as a positive Faecal Immunochemical Test (FIT).
Ongoing surveillance
For patients with a history of colorectal polyps, colorectal cancer or inflammatory bowel disease.
The reason for undergoing a colonoscopy and how often it is needed will depend on your symptoms, previous findings and individual risk factors.
Who Should Undergo a Colonoscopy?
Colonoscopy may be recommended earlier or more frequently for people at increased risk of colorectal cancer, including:
Individuals aged 50 and above
Colorectal cancer screening is recommended from age 50 for those at average risk.
Those with a family history of colorectal cancer
Particularly if a first-degree relative was diagnosed at a younger age.
Those with a history of colorectal polyps or cancer
Follow-up colonoscopies may be needed to check for new polyps or other changes.
Those with inflammatory bowel disease (IBD)
Long-standing Crohn’s disease or ulcerative colitis affecting the colon may increase colorectal cancer risk.
If you have any risk factors for colon cancer, speak to our doctors today for personalised advice on colonoscopy screening.
Speak to our colorectal specialist at 6262 1226 today
How to Prepare for a Colonoscopy?
Proper bowel preparation helps ensure the colon is clear so that the doctor can examine its lining accurately. Your doctor will provide specific instructions based on your procedure and medical history.
3–7 Days Before
- Follow any dietary instructions provided by your doctor, which may include avoiding high-fibre foods
- Inform your doctor about any medications or supplements you take, particularly blood thinners or iron supplements
- Do not stop or adjust any medication unless advised by your doctor
The Day Before
- Follow the recommended diet, which may include clear liquids such as water, clear broth or juice without pulp
- Take the prescribed bowel preparation solution according to your doctor's instructions
- Drink enough permitted fluids to stay hydrated
On the Day of Your Colonoscopy
- Complete any remaining bowel preparation as instructed
- Follow the fasting instructions provided by your doctor
- Take essential medications only as directed
- Arrange for someone to accompany you home, as you should not drive after sedation
By the end of the bowel preparation, your stools should generally be clear or pale yellow and watery. If your bowel preparation does not appear to be working as expected, contact the clinic for advice.
What to Expect During a Colonoscopy?
A colonoscopy is an outpatient procedure that typically takes around 20–40 minutes. It is usually performed under sedation for patient comfort.
During the procedure:
Sedation
Sedation is administered before the colonoscopy begins.
Examination
The colonoscope is guided through the colon to examine its lining for polyps or other abnormalities.
Polyp removal or biopsy
If necessary, polyps can be removed or tissue samples taken for further testing.
Recovery
After the procedure, you will be monitored while the effects of sedation wear off before being discharged.
What Happens After a Colonoscopy?
Immediately After the Procedure
You will be monitored while the effects of sedation wear off. Mild bloating, gas or abdominal discomfort may occur but usually settles within a few hours.
Eating and Returning to Normal Activities
Most patients can return to their usual diet and activities by the following day. If polyps were removed, your doctor may provide additional instructions on diet, medication or physical activity.
Getting Home Safely
Arrange for someone to take you home after the procedure, as sedation can temporarily affect your judgement and coordination. Avoid driving for the rest of the day.
When to Seek Medical Attention
Contact your doctor if you experience severe abdominal pain, persistent or heavy bleeding, fever or significant dizziness after your colonoscopy.
What Do the Results of My Colonoscopy Mean?
Your doctor will discuss the findings with you after the procedure. If a biopsy was taken or a polyp removed, the sample will be sent for laboratory testing.
If No Abnormalities Are Found
If no polyps or other abnormalities are found, your doctor will advise when your next screening is recommended based on your age and individual risk factors.
If Polyps or Abnormal Tissue Are Found
Polyps can often be removed during the colonoscopy and sent for further testing. If abnormal tissue is detected or biopsied, your doctor will discuss the results and whether further investigation, treatment or surveillance is needed.
What Are the Risks Involved in a Colonoscopy?
Colonoscopy is generally considered a safe procedure, although complications can occur. These may include:
Bleeding - This may occur after a biopsy or polyp removal and is usually minor.
Perforation - In rare cases, a small tear may occur in the wall of the colon.
Reaction to sedation - Some patients may experience side effects related to the medication used for sedation.
Our experienced team of colonoscopy doctors will ensure that you receive a safe and effective treatment.
Speak to our colorectal specialist at 6262 1226 today
Are There Alternatives to Undergoing Colonoscopy?
Depending on your symptoms and risk profile, other colorectal screening or diagnostic tests may be considered.
Faecal Immunochemical Test (FIT)
FIT is a non-invasive stool test that detects small amounts of blood in the stool. If the result is positive, further investigation with a colonoscopy is generally recommended.
CT Colonography
CT colonography uses CT imaging to examine the colon for polyps or other abnormalities. Unlike colonoscopy, it does not allow polyps to be removed or biopsies to be taken during the examination.
Flexible Sigmoidoscopy
Flexible sigmoidoscopy uses a flexible scope to examine the rectum and lower part of the colon. As it does not examine the entire colon, abnormalities in other areas may not be detected.
Colon Capsule Endoscopy
Colon capsule endoscopy uses a small camera contained within a capsule that is swallowed to capture images as it passes through the digestive tract. If abnormalities are detected, a conventional colonoscopy may still be required for biopsy or treatment.
Barium Enema
Using a barium enema involves inserting a tube into the anus and pouring a white barium solution in, coating the lining of the colon. This allows the colonic lining to become more clearly visible on an X-ray, highlighting any abnormalities that may be present. This procedure is seldom used now, in favour of CT Colonography.
FAQs on Colonoscopy
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Our Colonoscopy Specialists
Dr Dennis Koh
Medical Director & Senior Consultant Colorectal Surgeon
MBBS (Nottingham), B Med Sci (Nottingham), MMed (Surgery), FRCS (Edinburgh), FAMS
Dr Dennis Koh is a colorectal surgeon specialising in minimally invasive and advanced endoscopic techniques. He trained in Singapore and Switzerland, where he focused on proctology and pelvic floor disorders. A Fellow of the Royal College of Surgeons of Edinburgh and the Academy of Medicine, Singapore, Dr Koh is also passionate about teaching, having served as Assistant Professor at Duke-NUS and Clinical Senior Lecturer at NUS.
About Dr Dennis Koh
Dr Sharon Koh
Senior Consultant Colorectal Surgeon
MBBS (Singapore), MMed (Surgery), FRCS (Edinburgh), FAMS
Dr Sharon Koh is a fellowship-trained colorectal surgeon with expertise in minimally invasive surgery, advanced endoscopy, and inflammatory bowel disease. She trained in advanced colorectal surgery at Cedars-Sinai Medical Center (USA) and Japan. Formerly Director of Endoscopy at Alexandra Health, she also lectures at NUS and is an active member of local and international colorectal societies like the European Society of Coloproctology.
About Dr Sharon Koh
Dr Pauleon Tan
Senior Consultant Colorectal Surgeon
MBBS (Singapore), MMed (Surgery), FRCS (Edinburgh), FAMS
Dr Pauleon Tan is an experienced colorectal surgeon focusing on minimally invasive surgery, advanced endoscopy and cancer care. After receiving the MOH Health Manpower Development Plan award, he trained in Japan, where he mastered advanced techniques to improve cancer outcomes. Dr Tan has held key roles such as Clinical Director of the Colorectal Cancer Screening Programme at KTPH and is dedicated to delivering patient-centred care.
About Dr Pauleon Tan