Colonoscopy

A colonoscopy is a medical examination that allows doctors to examine the inner lining of the large intestine (colon) and rectum. During this procedure, a thin, flexible tube with a tiny camera at its tip is inserted through the rectum to view the entire colon. The procedure enables the detection of irritated tissue, ulcers, polyps, and cancer while allowing for tissue sample collection and removal of abnormal growths.

Dr. Chok Aik Yong

Colorectal Surgeon & General Surgeon

MBBS | MRCS (UK) | MMed (Surgery) | FRCS (UK)

Indications Benefits Techniques Preparation Procedure Recovery Risks FAQ

Indications for Colonoscopy

A colonoscopy is recommended in specific conditions and circumstances, including:

Abnormal Bowel Movements: Persistent changes in bowel habits, including diarrhoea, constipation, or changes in stool consistency lasting longer than four weeks, may indicate the need for a colonoscopy.
Rectal Bleeding: The presence of blood in stool or dark, tarry stools necessitates a colonoscopy to determine the source of the bleeding.
Unexplained Anaemia: Low iron levels or unexplained anaemia can indicate internal bleeding, which a colonoscopy can help identify and locate within the digestive tract.
Screening for Colorectal Cancer: Colonoscopy screening is recommended at age 45 for individuals with average risk, with follow-up intervals based on findings and personal risk factors.
Family History: Individuals with a family history of colorectal cancer or specific types of polyps are advised to begin colonoscopy screening at an earlier age and undergo it more frequently than those at average risk.

Benefits of Colonoscopy

Colonoscopy provides significant advantages for diagnosing, preventing, and treating digestive health conditions. These include:

Early Detection

Colonoscopy identifies precancerous polyps and early-stage cancers, offering the best chance for effective treatment and improved outcomes.
Prevention

By removing polyps during the procedure, colonoscopy can prevent them from progressing into colorectal cancer.
Accurate Diagnosis

The ability to directly visualise the entire colon enables precise identification of various conditions affecting the large intestine, including inflammation, ulcers, and tumours.
Immediate Treatment

Certain conditions, such as polyp removal or bleeding control, can be addressed during the same procedure, reducing the need for separate treatments.

Colonoscopy Techniques

Standard Colonoscopy

A flexible tube with a light and camera is used to examine the colon. The scope has channels for instruments to perform biopsies or remove polyps, enabling diagnosis and treatment during the same procedure. This method provides a real-time view of the colon lining, allowing immediate intervention when necessary.

Virtual Colonoscopy

This technique uses CT (computed tomography) scans to generate detailed 3D images of the colon. It requires bowel preparation but does not involve sedation or the insertion of a scope. While it effectively detects polyps and abnormalities, it cannot perform biopsies or remove polyps during the same session, necessitating additional procedures if abnormalities are found.

Chromoendoscopy

A dye solution is applied to the colon lining during the examination to enhance visualisation. The dye highlights subtle tissue changes, improving the detection of flat polyps or early cancerous changes. This technique is particularly useful for identifying areas requiring closer examination or biopsy.

Procedure Preparation

Medical Evaluation: A thorough health assessment includes reviewing medical history, current medications, and any previous surgical procedures. Your doctor will perform a physical examination and may request blood tests to assess your overall health status. This evaluation helps determine any specific precautions needed during the procedure.
Medication Adjustments: Blood-thinning medications may need to be temporarily stopped before the procedure. Inform your doctor about all medications, including over-the-counter drugs and supplements. Some medications require adjustment or temporary discontinuation based on your specific health needs.
Dietary Restrictions: A clear liquid diet begins 24-48 hours before the procedure. This includes water, clear broths, tea without milk, and clear fruit juices without pulp. Red or purple liquids should be avoided as they can interfere with the examination.
Bowel Preparation: The colon must be completely empty for accurate examination. This involves taking prescribed laxatives and following specific timing instructions. The preparation typically begins the day before the procedure and may require drinking a large amount of cleansing solution.

Step-by-Step Procedure

Sedation Administration

Sedation is provided to keep you comfortable during the procedure. A sedative and pain medication is administered through an intravenous line while you are positioned on your left side. Monitoring devices track your vital signs throughout.

Scope Insertion

The doctor gently inserts the colonoscope through the rectum and advances it through the large intestine. Air or carbon dioxide is introduced to inflate the colon, providing better visibility of the intestinal lining.

Colon Examination

The colonoscope is carefully guided through the entire length of the colon. The doctor examines the intestinal lining thoroughly during both insertion and withdrawal of the scope, looking for any abnormalities.

Tissue Sampling and Polyp Removal

If abnormal areas or polyps are detected during the examination, they can often be addressed immediately. Specialised instruments passed through the colonoscope allow for the collection of tissue samples and the removal of polyps. These are then sent for laboratory analysis to assess their characteristics and guide any necessary follow-up treatment.

Scope Withdrawal

As the colonoscope is slowly withdrawn, the lining of the colon is re-examined to ensure no abnormalities or polyps are missed. Any remaining air or gas introduced during the procedure is gently suctioned to minimise discomfort and ease recovery.

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Post-Procedure Care and Recovery

Immediate Recovery

After the procedure, patients are monitored for 30–60 minutes as the effects of sedation gradually wear off. Mild bloating or gas, caused by the air introduced during the colonoscopy, is common and can often be relieved by gentle walking.

Diet Resumption

A regular diet can be resumed gradually after the procedure. Start with light, easily digestible foods such as soup, crackers, or toast. Avoid heavy, greasy, or spicy foods until your digestive system feels normal. Alcohol should be avoided for at least 24 hours.

Activity Guidelines

Rest is advised following the procedure. As sedation effects may persist, arrange for someone to accompany you home. Avoid driving, strenuous activities, or operating heavy machinery for 24 hours. Most patients can resume their everyday routines the following day.

Potential Risks and Complications

While colonoscopy is generally safe, it does carry some risks. Bleeding may occur, particularly after polyp removal, but it typically resolves without intervention. In very rare cases, the colon wall may be perforated, requiring surgical repair. Infections are uncommon, and some individuals may experience mild abdominal discomfort or temporary changes in bowel habits for a few days after the procedure.

Frequently Asked Questions (FAQ)

Can a colonoscopy detect all types of cancer?

A colonoscopy is highly effective in detecting colorectal cancer and precancerous polyps. However, it does not identify cancers outside the colon or rectum. If other gastrointestinal cancers are suspected, additional diagnostic tests may be recommended.

Is a colonoscopy painful?

A colonoscopy is generally not painful for most patients. Some mild discomfort, like bloating or cramping, may occur but usually subsides within a few hours after the procedure.

When will I receive my results?

Preliminary findings are shared immediately after the procedure. Detailed results are generally available within 7 to 10 days if biopsies were taken. Your doctor will discuss the findings and any necessary follow-up.

How often do I need a colonoscopy if polyps are found?

If polyps are detected, your doctor will recommend a follow-up colonoscopy based on the size, number, and type of polyps. In many cases, follow-up is recommended within 3 to 5 years to monitor for recurrence or new growth.

Dr. Chok Aik Yong

Colorectal Surgeon & General Surgeon

MBBS|MRCS (UK)|MMed (Surgery)|FRCS (UK)

Expertise lies in managing colorectal diseases, particularly advanced colorectal cancer and inflammatory bowel disease.

Dr Chok graduated with degrees in Bachelor of Medicine and Surgery from the National University of Singapore. He was conferred the Master of Medicine (Surgery) in Edinburgh (UK) and a member of the Royal College of Surgeons, UK. He subsequently completed his specialist training in colorectal surgery and became a Fellow of the royal college of Surgeons in Edinburgh in 2016.
Dr Chok was awarded the Health Manpower Development Plan (HMDP) award in 2019 to further advance his colorectal training at Royal Marsden Hospital, one of the top 5 cancer centres in the world. While in London, Dr Chok trained with pioneers in the surgical management of advanced colorectal cancer and inflammatory bowel disease (IBD) and gained extensive experience while appraising the latest clinical and research evidence.

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