What Is a Colonoscopy?

A colonoscopy is a screening procedure that allows for the direct, real-time visualisation of the colon and rectum. This procedure uses a device known as a colonoscope, a flexible long tube with a small light and camera on one end. The primary purpose of a colonoscopy is to help detect abnormalities, such as colorectal cancer or polyps.

Benefits of Colonoscopy Screening

A colonoscopy has several advantages:

Early Detection of Colon Cancer

A colonoscopy can detect early signs of colorectal cancer, increasing the chances of successful treatment.

Decreased Risk for Colon Cancer

By identifying and removing precancerous polyps, a colonoscopy can effectively reduce the risk of developing colon cancer.

Improved Diagnosis

A colonoscopy provides a clear visualisation of the colon, which aids in diagnosing gastrointestinal diseases.

Detection of Other Illnesses

A colonoscopy can also detect other issues, such as diverticula (pouches along the colon) and signs of inflammatory bowel disease.

Treatment and Prevention

A unique advantage of a colonoscopy is its ability to treat certain abnormalities on the spot, such as removing polyps.

High Accuracy

A colonoscopy is known for its high accuracy in detecting abnormalities in the colon.

Quick and Pain-Free Process

A colonoscopy is usually performed under sedation to ensure patient comfort.

What Conditions Can a Colonoscopy Diagnose?

A colonoscopy is a valuable diagnostic tool that can identify various conditions affecting the colon and rectum, including:

Colorectal Cancer

A colonoscopy is one of the most effective ways to detect early stages of colorectal cancer. It can identify small polyps (abnormal growths), which could, over time, develop into cancer.

Inflammatory Bowel Disease (IBD)

Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, cause chronic inflammation in the digestive tract. A colonoscopy can detect signs of these conditions, including ulcers, inflammation, and bleeding.

Diverticulosis and Diverticulitis

These conditions occur when small pouches (diverticula) form in the colon's walls and become inflamed or infected. A colonoscopy can reveal these pouches and assess their condition.

Gastrointestinal Bleeding

Unexplained bleeding in the digestive tract can often be traced back to the colon or rectum through a colonoscopy.

Irritable Bowel Syndrome (IBS)

Although a colonoscopy cannot directly diagnose IBS, it can rule out other conditions like IBD or cancer that might mimic IBS symptoms.

Polyps and Tumours

Colonoscopies can help identify precancerous polyps and tumours in the colon and rectum, which can be removed during the procedure.

Who Needs to Get a Colonoscopy?

A colonoscopy is generally recommended for people with the following risk factors:


In Singapore, routine colonoscopies are recommended for individuals aged 50 and above. Earlier screening is recommended for higher-risk individuals.

Family History

If you have a family history of colorectal cancer or polyps, you may need to start screening earlier. The usual recommendation is to have your first colonoscopy at age 40 or 10 years before the age at which your family member was diagnosed.


If you are experiencing rectal bleeding, persistent abdominal pain, unexplained weight loss, or changes in bowel habits, a colonoscopy can help diagnose the cause.

Previous Polyps or Colorectal Cancer

Individuals who have had polyps or colorectal cancer in the past are more likely to develop these conditions again.

Certain Genetic Syndromes

People with certain genetic syndromes, such as familial adenomatous polyposis (FAP) or Lynch syndrome, may need to start colonoscopy screenings at a younger age and have them more often.

How to Prepare for a Colonoscopy

Colon cleansing is an important part of the preparation for colonoscopy. An improperly prepared colon can prevent the gastroenterologist from clearly seeing the inside of your colon and could result in the need to repeat the procedure. Proper preparation includes:

Medication Adjustment

You may be advised to temporarily stop taking certain medications which may pose risks to the procedure.

Dietary Restrictions

You may be asked to limit or avoid solid foods for a few days before the test.

Colon Cleansing

You will need to take a strong laxative so that your doctor can view and access the entirety of your colon during the procedure.

Drinking Clear Liquids

You will be advised to drink only clear liquids the day of your colonoscopy.

The Colonoscopy Procedure

A colonoscopy is an outpatient procedure that may take around 20-40 minutes to complete. Here is what to expect:


Before the procedure starts, you will be given a sedative to help you relax and not feel any discomfort during the procedure.

Insertion of the Colonoscope

The doctor will insert the colonoscope into your rectum. The scope has a light and a camera on one end that displays images on a monitor.


The doctor carefully inserts the colonoscope to inspect the lining of your colon. Air or carbon dioxide will be introduced through the scope to inflate the colon for better visibility.

Polyp Removal or Biopsy

Any polyps found can be removed during the procedure. Likewise, a biopsy can be taken if other abnormal tissues are found.

Recovering from a Colonoscopy

After a colonoscopy, patients are moved to a recovery room where they will stay until the effects of the sedation begin to wear off. This usually takes about an hour. It is important to arrange for someone to take you home afterwards.

Mild discomfort, such as gas, bloating, or mild cramping, is normal after a colonoscopy. These symptoms should go away within 24 hours. You might also feel bloated or have stomach cramps for 2 to 3 hours after the procedure. Some patients may also notice blood in their stool or bleeding from the rectum, particularly if a biopsy or polyps were removed.

Rest is recommended for the remainder of the day, and normal activities can generally be resumed the next day. If biopsies or polyps were removed, your doctor might suggest a special diet for a day or two to aid intestinal healing. Additionally, ample fluid intake is recommended to replenish lost fluids from the preparation process.

Follow-up and Interpretation of Results

After your colonoscopy, your doctor will discuss the initial results with you. However, if biopsies or polyps were taken, they need to be analysed in a lab, which may take longer.

Depending on the findings, your doctor will advise you on follow-up steps. If no issues are detected and you have no other risk factors, your doctor might suggest a colonoscopy again in ten years. However, if polyps were removed or if you have other risk factors, a follow-up colonoscopy may be recommended sooner.

Frequently Asked Questions (FAQs)

Is a colonoscopy painful?

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Meet Our Specialist

Dr Kieron Lim

MBBS, University of LondonMember, Royal College of Physicians (UK)Fellow, Academy of Medicine (Gastroenterology) SingaporeFellow, Royal College of Physicians (Edinburgh)

Dr Kieron Lim is a senior consultant specialising in Gastroenterology and Hepatology, providing comprehensive care for patients with gastrointestinal conditions in Singapore. His expertise extends to disorders affecting the oesophagus, stomach, colon, liver, pancreas, and gallbladder. Through his experience, Dr Lim enhances patient outcomes by facilitating early detection and timely medical interventions.