A colonoscopy is used to examine the large bowel for bleeding, inflammation, polyps, tumours and other abnormalities.
During the procedure, a doctor passes a thin, flexible tube with a small camera through the anus and into the large bowel. This allows the lining of the bowel to be examined directly. If abnormal tissue is found, a sample may be taken for laboratory testing. Polyps may also be removed during the procedure when appropriate.
A positive faecal immunochemical test, commonly known as a FIT, does not mean that you have colorectal cancer. However, further investigation may be required to identify the cause of the bleeding.
You should consult a doctor if you experience:
These symptoms should be assessed regardless of your age. People with a history of colorectal polyps, inflammatory bowel disease or a family history of colorectal cancer may also need to begin screening earlier or undergo regular colonoscopy.
The Hong Kong Government subsidises colorectal cancer screening for eligible Hong Kong residents aged between 50 and 75 who do not have symptoms of colorectal cancer.
Participants first undergo a faecal immunochemical test every two years. Those with a positive result are referred for a government-subsidised colonoscopy. In 2026, eligible residents are those born between 1950 and 1976.
Before the procedure, you will need to adjust your diet, take bowel preparation medication and fast according to the instructions provided by the clinic or hospital. Thorough bowel cleansing is essential because remaining stool can obstruct the view of the bowel lining and affect the accuracy of the examination.
Tell your doctor about any regular medication you take, particularly blood-thinning medication, diabetes medication and iron supplements. Do not stop taking prescribed medication unless instructed to do so.
If you receive sedation, you should arrange for someone to accompany you home and avoid driving for the period advised by your healthcare team.
Seek medical attention after the procedure if you experience heavy or persistent bleeding, severe abdominal pain, fever or continuing abdominal swelling.
A colonoscopy may cause bloating, an urge to open your bowels or temporary abdominal discomfort. Sedation or pain relief may be offered where appropriate.
Although serious complications are uncommon, colonoscopy is an invasive procedure and carries a small risk of bleeding, bowel perforation and reactions to sedation. Your doctor will explain the benefits and individual risks before the examination.
