Colonoscopy

What is a colonoscopy?

A colonoscopy is a medical procedure that allows doctors to closely examine the inside of the large intestine (colon) and rectum using a long, thin, flexible tube called a colonoscope. The colonoscope is equipped with a small camera and light at its tip, which transmits high-resolution images to a monitor in real time. This enables the doctor to assess the lining of the bowel for any signs of inflammation, abnormal growths, ulcers, bleeding, or early signs of colorectal cancer.

Colonoscopy is mainly used for evaluating bowel symptoms and detecting colorectal conditions, particularly because it offers both diagnostic and therapeutic capabilities. In addition to visual inspection, the procedure allows for the removal of polyps (polypectomy), the collection of tissue samples (biopsies), and the treatment of minor bleeding, all during the same session.

This procedure is commonly recommended for people experiencing symptoms such as rectal bleeding, persistent changes in bowel habits, unexplained abdominal pain, or as part of routine screening for colorectal cancer, especially in individuals aged 50 and above or those with a family history of bowel disease.

Why is a colonoscopy performed? 

A colonoscopy is carried out to investigate symptoms affecting the lower digestive tract, screen for colorectal cancer, and manage existing bowel conditions. It is one of the most effective ways to detect problems in the colon early, often before symptoms become severe or complications arise.

Common reasons for undergoing a colonoscopy include:

• Rectal bleeding — to identify the source of bleeding, which may be caused by haemorrhoids, polyps, or more serious conditions.

• Changes in bowel habits — such as persistent diarrhoea, constipation, or a noticeable change in stool consistency or frequency.

• Abdominal pain or bloating — especially if unexplained or persistent.

• Unexplained weight loss or anaemia — to check for internal bleeding or tumours in the colon.

• Family or personal history of bowel disease — including colorectal cancer, polyps, or inflammatory bowel disease (IBD).

• Routine cancer screening — recommended from the age of 50, or earlier for those at higher risk, to detect pre-cancerous polyps or early cancer.

• Monitoring — to monitor individuals with a history of polyps, bowel surgery, or chronic inflammatory bowel conditions like ulcerative colitis or Crohn’s disease.

Colonoscopy provides a direct view of the bowel lining, allowing doctors to detect and remove abnormal tissue during the same procedure, which makes it a vital tool in both diagnosis and prevention.

How to prepare for a colonoscopy? 

Proper preparation is essential to ensure that the colon is clean and visible during the procedure. This allows the doctor to examine the bowel lining thoroughly and reduces the risk of missing important findings. Your healthcare team will provide detailed instructions tailored to your specific needs, but general preparation typically includes the following:

• Bowel cleansing (laxatives) — you will be asked to take a strong laxative the day before the procedure to empty your bowels completely. This may involve drinking a solution over a few hours, sometimes in split doses.

• Dietary changes — a low-fibre diet is often recommended for a few days before the test, followed by clear fluids only the day before. You must not eat or drink anything for several hours before the procedure.

• Medication adjustments — inform your doctor about all medications, especially blood thinners, diabetes treatment, or iron supplements, as you may need to pause or adjust some of them.

• Allergies and health conditions — let the medical team know if you have any allergies, heart or kidney problems, or other medical concerns.

• Transportation arrangements — if you are having sedation, you must arrange for someone to accompany you and take you home, as you will not be able to drive or travel alone afterwards.

Following the preparation instructions carefully is vital for a successful and accurate colonoscopy. If the bowel is not properly cleared, the procedure may need to be postponed or repeated.

What happens during a colonoscopy?

A colonoscopy is usually performed as a day procedure, so you can go home the same day. It is typically done under sedation to ensure you are comfortable and relaxed throughout the examination. The procedure itself usually takes around 20 to 45 minutes, depending on whether any treatment is required.

During the procedure:

• Sedation — you will be given a sedative through a small drip in your arm to help you feel drowsy and comfortable. In some cases, light sedation or gas and air may be used instead.

• Positioning — you will lie on your side with your knees drawn up, and a monitor will be used to track your heart rate, blood pressure, and oxygen levels.

• Insertion of the colonoscope — the doctor will gently insert the lubricated colonoscope through your back passage and slowly guide it along the colon. Air or carbon dioxide is introduced to expand the bowel, which helps provide clearer views.

• Inspection and imaging — the camera on the tip of the colonoscope transmits live images to a screen, which enables the doctor to examine the bowel lining in detail.

• Biopsies and treatment — if needed, small instruments can be passed through the scope to take tissue samples, remove polyps, stop bleeding, or perform other treatments.

• Completion — once the inspection is complete, the scope is carefully withdrawn, and you will be moved to a recovery area until the effects of the sedation wear off.

Although the procedure may cause some bloating or cramping due to the air used, most patients tolerate it well and have no memory of the test afterwards due to the sedation.

What are the benefits of a colonoscopy? 

Colonoscopy is one of the most comprehensive procedures available for assessing the health of the colon and rectum. It offers both diagnostic clarity and immediate therapeutic options in a single session, which makes it an essential tool in modern gastrointestinal care.

Key benefits include:

• Early detection of bowel cancer — colonoscopy can identify colorectal cancer at an early, more treatable stage, even before symptoms develop.

• Removal of polyps — pre-cancerous polyps can be detected and removed during the same procedure, which minimises the risk of cancer developing later.

• Accurate diagnosis — it allows direct visual inspection of the bowel lining to diagnose conditions such as inflammatory bowel disease (IBD), diverticulosis, or unexplained bleeding.

• Targeted biopsies — tissue samples can be taken for laboratory analysis to confirm or rule out specific conditions without the need for surgery.

• Therapeutic interventions — in addition to diagnosis, it can treat certain issues such as bleeding, narrowing (strictures), or foreign bodies in the colon.

• Observation — it helps monitor people with a history of polyps, bowel disease, or cancer to detect changes early and guide future care.

By identifying abnormalities before they cause significant harm, colonoscopy plays a crucial role in prevention, early intervention, and improved long-term outcomes.

What are the risks of a colonoscopy?

Colonoscopy is generally a safe and well-tolerated procedure, especially when performed by an experienced endoscopist. However, like all medical procedures, it carries a small risk of complications. Your doctor will discuss these with you beforehand and ensure all necessary precautions are taken.

Potential risks include:

• Discomfort or bloating — it is common to feel mild cramping or a sense of fullness due to air introduced during the procedure; this usually passes within a few hours.

• Bleeding — minor bleeding can occur, particularly if a polyp is removed or a biopsy is taken. This is usually self-limiting but may occasionally require further treatment.

• Perforation — a rare but serious risk where a small tear develops in the bowel wall. This may require surgery, but the risk is very low (fewer than 1 in 1,000 procedures).

• Reaction to sedation — some people may experience drowsiness, nausea, or breathing changes from the sedative, but monitoring during the procedure ensures your safety.

• Incomplete examination — in a small number of cases, the colonoscope may not reach the entire length of the colon, which may require a repeat procedure or alternative investigation.

The benefits of colonoscopy, especially in detecting cancer early or removing polyps, usually far outweigh the small risk of complications. Your doctor will assess your personal risk factors and guide you accordingly.

What to expect after a colonoscopy? 

Most people recover quickly after a colonoscopy, particularly if no complications arise. Full recovery is usually swift, with most patients able to resume normal activities by the next day.

After the procedure:

• Sedation recovery — if you were given sedation, you may feel drowsy or groggy for several hours. You must not drive, operate machinery, or make important decisions for at least 24 hours.

• Abdominal discomfort — mild bloating, wind, or cramping is common due to the air used to inflate the bowel. These symptoms usually pass within a few hours.

• Eating and drinking — you can generally eat and drink as normal after the procedure, unless your doctor advises otherwise. Start with light meals if your stomach feels unsettled.

• Results — the doctor may discuss initial findings with you before discharge. If any biopsies were taken or polyps removed, results are usually available within a week and may be shared during a follow-up appointment or through your referring doctor.

• Return to daily activities — most people feel well enough to return to work and normal routines the following day, especially if no sedation was used.

You should seek medical advice immediately if you experience ongoing abdominal pain, heavy rectal bleeding, fever, or vomiting, as these may indicate a rare complication.

Summary 

Colonoscopy is a safe, highly effective procedure that enables doctors to examine the lining of the colon and rectum in detail. It plays a crucial role in diagnosing and treating a wide range of bowel conditions, from inflammation and polyps to early-stage cancer. With the ability to detect problems early and even treat them during the same session, colonoscopy remains the most preferred method for bowel screening and gastrointestinal investigation.

The procedure is typically performed as a day case under sedation and is well tolerated by most patients. It also provides peace of mind for those with persistent symptoms or a family history of colorectal disease. Whether you are experiencing changes in bowel habits, unexplained abdominal pain, rectal bleeding, or have been advised to undergo routine screening, colonoscopy offers a reliable and thorough evaluation of your bowel health.

If you have bowel-related symptoms or are due for a screening test, schedule a consultation with Tan Siong San Surgery for expert assessment, timely diagnosis, and personalised care.

Frequently Asked Questions (FAQs)