- Early Detection: Colonoscopy identifies precancerous polyps and early-stage colorectal cancer when treatment outcomes are most favourable.
- Prevention: During the procedure, doctors can remove polyps before they potentially develop into cancer, effectively preventing disease progression.
- Accurate Diagnosis: The direct visualisation of the colon aids in the accurate identification of various conditions affecting the large intestine.
- Immediate Treatment: Some conditions can be treated during the same procedure, eliminating the need for additional interventions.
Colonoscopy
Dr Chong Choon Seng
MBBS | MRCS | Masters in Medicine (Surgery) | FRCS (Edinburgh)
A colonoscopy is a procedure that examines the large intestine (colon) and rectum using a flexible tube with a small camera. It is performed to investigate symptoms such as abdominal pain or rectal bleeding and to screen for conditions such as colorectal cancer, polyps, or inflammation. The procedure allows doctors to inspect the colon’s inner lining, take tissue samples for testing, and remove small growths like polyps if necessary.
Indications for Colonoscopy
A colonoscopy may be recommended as a diagnostic or screening tool for various conditions and symptoms.
- Routine Cancer Screening: Adults aged 45 and older undergo colonoscopy screening every 10 years to detect early signs of colorectal cancer.
- Unexplained Bleeding: Patients with rectal bleeding or blood in stool require colonoscopy to identify the source and determine appropriate treatment.
- Changes in Bowel Habits: Persistent changes in bowel movements, including diarrhoea or constipation lasting more than a few weeks, warrant examination through colonoscopy.
- Chronic Abdominal Pain: Unexplained abdominal pain or discomfort may necessitate colonoscopy to evaluate for underlying conditions affecting the colon.
- Family History: Individuals with a family history of colorectal cancer or certain inherited conditions undergo earlier and more frequent colonoscopy screenings.
- Follow-up Examination: Patients with previous polyps or colon cancer receive regular colonoscopies to monitor for recurrence.
Benefits of Colonoscopy
Colonoscopy offers several advantages as both a diagnostic and preventive procedure.
Types of Colonoscopy Techniques
The choice of colonoscopy technique depends on specific medical requirements and diagnostic needs.
Standard Colonoscopy
The most common technique uses a long, flexible colonoscope inserted through the rectum. The scope contains a light source, camera, and channels for instruments. This method allows for complete examination of the colon, tissue sampling, and polyp removal in a single procedure. The real-time video feed enables doctors to examine the intestinal lining in detail.
Virtual Colonoscopy
This technique uses CT scanning to create detailed 3D images of the colon. The procedure requires bowel preparation but no sedation. A small tube inflates the colon with air while CT images are taken. Virtual colonoscopy serves as an alternative for patients who cannot undergo traditional colonoscopy, though it cannot remove polyps or take biopsies.
Chromoendoscopy
This enhanced visualisation technique involves spraying special dyes in the colon during the procedure. The dyes highlight subtle changes in the intestinal lining, making it easier to detect small polyps or abnormal growths. This method particularly helps in screening patients with inflammatory bowel disease or hereditary conditions.
Procedure Preparation
Medical Evaluation
Your doctor reviews your medical history, current medications, and any allergies. A physical examination and blood tests assess your fitness for the procedure. The evaluation identifies potential risks and determines the most appropriate bowel preparation method.
Medication Adjustments
Certain medications require temporary discontinuation before the procedure. Blood thinners, iron supplements, and some diabetes medications may need adjustment.
Dietary Modifications
A clear liquid diet begins 24-48 hours before the procedure. Approved liquids include water, clear broth, coffee or tea without milk, and clear juice. Red or purple liquids must be avoided as they can interfere with the examination.
Bowel Preparation
Complete colon cleansing occurs the day before the procedure. The preparation involves drinking a special solution that causes diarrhoea to empty the colon.
Step-by-Step Procedure
Sedation Administration
Intravenous sedation is administered to ensure comfort during the procedure. The medication induces a light sleep-like state while maintaining natural breathing, with the sedation level adjusted to individual needs.
Colonoscope Insertion
The lubricated colonoscope is gently inserted through the rectum into the colon. To enhance visibility, air or carbon dioxide inflates the colon. The scope advances gradually as the intestinal lining is examined.
Colon Examination
The colonoscope traverses the entire colon, reaching its junction with the small intestine. A camera on the scope transmits high-resolution images to a monitor, enabling a detailed examination of the intestinal wall. Findings are documented, and photographs are taken as needed.
Tissue Sampling/Polyp Removal
If abnormalities are identified, specialised instruments can be passed through the colonoscope to collect tissue samples or remove polyps. These samples are sent to a laboratory for analysis. The removal technique varies depending on the polyp’s size and type.
Scope Withdrawal
The colonoscope is carefully withdrawn while a final examination is conducted. This phase often provides the most detailed view of the colon. Any remaining air or gas is suctioned out to reduce discomfort.
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Post-Procedure Care and Recovery
- Immediate Recovery: After the procedure, patients are monitored in a recovery area until the effects of sedation wear off, typically for 30 to 60 minutes. Vital signs are observed until they stabilise. Mild cramping or bloating may occur as residual air exits the colon.
- Diet and Rest: A regular diet can be resumed gradually, starting with clear liquids and transitioning to solid foods as tolerated. Resting at home is recommended to allow full recovery from sedation. Normal bowel movements generally return within 1 to 2 days.
- Resuming Activities: Most individuals can return to normal activities the day after the procedure. Exercise and strenuous activities should be avoided until at least 24 hours have passed. Work can usually resume the following day unless complications arise.
- Follow-up Care: The findings from the procedure are reviewed before discharge. If tissue samples or polyps were removed, results are typically available within 1 to 2 weeks. Based on the findings, follow-up appointments and future screenings are scheduled as needed.
Potential Risks and Complications
Colonoscopy is generally safe but has some risks. Bleeding may occur, particularly after polyp removal, but it usually resolves without treatment. In rare cases, colon wall perforation may occur and require surgical repair. Infection is uncommon, and some individuals may experience mild abdominal discomfort or temporary changes in bowel habits for a few days afterward.
Frequently Asked Questions
How long does bowel preparation take?
The complete bowel preparation process takes 24-48 hours. The most intensive phase occurs in the evening before the procedure, when you take the prescribed laxative solution. Most patients complete the preparation by midnight before their appointment.
How often should I have a colonoscopy?
The recommended frequency depends on factors such as your age, medical history, family history, and individual risk factors. Routine screenings are generally advised every 10 years starting at age 45, but individuals at higher risk, such as those with a family history of colorectal cancer or previous polyps, may need more frequent examinations.
What are the alternatives if I cannot undergo a colonoscopy?
If a colonoscopy is not possible, alternatives include virtual colonoscopy (CT colonography), stool-based tests, and flexible sigmoidoscopy. However, these alternatives may have limitations, such as an inability to remove polyps or take tissue samples.
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Dr Chong Choon Seng
MBBS (NUS)
MRCS (Edinburgh)
Masters in Medicine (Surgery)(NUS)
FRCS (Edinburgh)
Dr Chong is the former Program Director of General Surgery Residency at NUHS, and has more than 10 years of experience as a colorectal and general surgeon.
As an esteemed professional in minimally invasive surgery, Dr. Chong remains committed to achieving optimal outcomes for all surgical conditions, from piles to cancer treatment.
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