A colonoscopy is a simple and routine medical procedure that examines the inner lining of the
large intestine or colon and rectum using a flexible scope with a built-in camera and light at
the end. This procedure allows doctors to inspect the colon for unusual growths, inflammation,
or other abnormalities. When necessary, small tissue samples (biopsies) can be taken for further
examination.
Having direct visualisation of the colon's inner lining, a colonoscopy can detect indications of
early-stage colorectal cancer or other gastrointestinal diseases that might otherwise go
unnoticed. This can also serve as a therapeutic procedure, where the doctor locates and removes
potential precancerous polyps or growths in a single session.
Some common gastrointestinal conditions that can be diagnosed through a colonoscopy include:
One of the primary reasons for colonoscopies is colorectal cancer, which develops on
the inner walls of the colon and rectum. It typically begins as benign polyps, but
they can turn into cancerous lesions if left undetected. In Singapore, colorectal
cancer is the second most common cancer, with about 7 new cases reported every day.
In its initial stages, colorectal cancer often develops silently, with most cases
having few or no visible symptoms until the disease has advanced. Fortunately, a
colonoscopy screening can identify and eliminate potentially cancerous growths while
they are still localised. For more advanced cases, a colonoscopy helps in assessing
the extent of the cancer and determining the appropriate treatment strategy.
Polyps are abnormal growths that appear along the inner lining of the colon or
rectum. They vary in size and shape and are classified into different types. Some
polyps, such as hyperplastic polyps, are benign with a very low risk of becoming
malignant. On the other hand, adenomatous polyps—the most common type of polyp—may
progress into cancer over time.
Colonoscopy is a reliable diagnostic tool to detect different types of colorectal
polyps. During the procedure, the doctor may remove the polyps for further
examination under a microscope. This removal can significantly lower the risk of
colorectal cancer by removing growths before they turn into aggressive tumours.
Inflammatory bowel disease (IBD) refers to a group of chronic conditions
characterised by inflammation and damage to the gastrointestinal tract. There are
two main types of IDB: ulcerative colitis and Crohn’s disease. Ulcerative colitis
targets the colon and rectum, causing continuous inflammation, while Crohn's disease
can occur in any part of the gastrointestinal tract, causing patches of
inflammation.
Early detection of IBD is crucial in preventing serious complications like bowel
obstruction and perforation. With a colonoscopy, doctors can identify signs of IBD,
such as swollen tissue, cancer growth, and ulcers. Sometimes, a biopsy might be
taken to confirm the diagnosis and guide treatment decisions.
Diverticulosis occurs when small, bulging pouches, known as diverticula, form within
the muscle of the colon wall. While many individuals with diverticulosis remain
asymptomatic, some cases may progress into diverticulitis, an inflammation or
infection caused by the abnormal pouches. This condition can be painful and may lead
to serious complications, such as abscesses or perforations.
A colonoscopy allows doctors to evaluate the colon's function, confirm the presence
of diverticular disease, and rule out other potential underlying issues like colon
cancer. In cases of acute diverticulitis, the colonoscopy procedure is typically
delayed for at least 6–8 weeks until the acute phase is resolved to minimise the
risk of complications.
Colonic strictures are narrowed segments in the colon that can significantly affect
stool passage and bowel function. These narrowed areas may result from several
factors, such as scarring from IBD, complications from previous surgery, or abnormal
growths.
A colonoscopy is an essential tool used to visualise the colon and pinpoint the root
causes of intestinal blockages. This examination enables doctors to implement
immediate medical treatments to alleviate symptoms and prevent further damage or
complications from occurring.
Haemorrhoids, or piles, are swollen blood vessels in the inner lining of the rectum
and on the surface of the anus. These swollen blood vessels can develop around the
anus (external piles), causing itchiness, discomfort, or swelling. Sometimes, they
may develop inside the rectum (internal piles), which are often difficult to see or
feel. Although internal piles typically are painless, they can sometimes cause
bleeding due to straining during bowel movements.
While most haemorrhoids are diagnosed through a digital rectal examination or
proctoscopy/anoscopy, a colonoscopy can be performed to visualise the rectum lining
and check for internal haemorrhoids. This procedure can also help distinguish
haemorrhoids from other conditions with similar symptoms (e.g., heavy or persistent
bleeding).
Apart from routine screenings, doctors may recommend a colonoscopy if you are experiencing:
- Persistent abdominal pain, gas, or bloating
- Blood or mucous in the stool
- Changes in bowel habits, such as recurrent diarrhoea or constipation
- Sudden, unexplained weight loss
- Rectal bleeding
How often an individual should undergo colonoscopy screenings depends on the findings, individual
risk factors, and medical history.
According to MOH guidelines, individuals with an average risk should begin screening between the
ages of 45 and 50. After the initial screening, subsequent screenings should be conducted every 10
years.
For high-risk individuals—such as those with a family history of colorectal cancer or polyps—doctors
may recommend starting routine colonoscopy screenings earlier than the standard guideline. For
example, if a first-degree relative was diagnosed with colorectal cancer, screening should typically
begin either at age 40 or 10 years before the relative’s age at diagnosis, whichever comes first.
Early detection of colorectal conditions through colonoscopy offers several advantages, such as:
- Improved Treatment Outcomes: A colonoscopy can detect colorectal cancer at an early stage, providing a chance for timely intervention and improved prognosis. Any precancerous polyps found can be removed on the spot to prevent cancer development effectively.
- Comprehensive Colon Examination: Colonoscopy provides a complete view of the entire colon and rectum, allowing thorough evaluation and reducing the risk of missed abnormalities.
- Reduced Risk of Complications: Colonoscopy is the most precise technique for identifying colorectal problems. By performing this procedure, it is possible to prevent cancer progression and severe complications, such as obstruction or perforation of the bowel, from developing.
A colonoscopy is an effective and accurate screening method for colorectal cancer detection, particularly in its initial stage. This procedure can detect more than 95% of colorectal cancers as well as precancerous polyps.
A colonoscopy is generally done under sedation, keeping patients comfortable and pain-free throughout the procedure. While it is common to experience minor discomfort such as slight bloating, cramping, or even traces of blood in bowel movements following the examination, these symptoms are usually temporary and resolve quickly.
Colonoscopies may be unsuitable for individuals aged 75 and above with underlying
health issues like heart disease or lung problems due to the required bowel
preparations and associated risks.
In such cases, doctors may provide alternative screening methods, such as a faecal
immunochemical test (FIT) or CT colonography, to ensure proper evaluation without
the need for a colonoscopy.