ARTICLE

Colorectal Cancer Prevention Guide: Early Symptoms and Screening

14-min read

Updated on 2026-5-19

Author: AIA Content Editorial Team

A healthcare professional explaining and showing medical records to a patient in a clinical setting, representing colorectal cancer symptoms and screening methods.

Colorectal cancer is one of the most common and deadly cancers in Hong Kong,¹ and there is growing concern over its increasingly younger age of onset.² However, early-stage colorectal cancer often presents with no obvious symptoms, making it easy to overlook. Understanding the early warning signs of colorectal cancer, its major risk factors, and the importance of regular screening can help with colorectal cancer prevention. This article explains the causes of colorectal cancer, prevention strategies, and related protection planning considerations.

Why Colorectal Cancer Deserves Attention in Hong Kong: Local Trends and Younger Onset

The Third Most Common Cancer in Hong Kong: Latest Overview

According to the latest data from the Hong Kong Cancer Registry under the Hospital Authority, colorectal cancer remains one of the most common cancers in Hong Kong, with 5,467 new cases recorded in 2023.³

A Younger-Onset Trend: Why It Is No Longer Just an "Older Person's Disease"?

In the past, colorectal cancer was widely seen as a disease that mainly affected people aged 50 or above. However, recent evidence suggests that the age of onset is gradually becoming younger.² Modern lifestyles often involve high levels of work and daily stress, prolonged sitting in office environments, and a preference for high-fat, low-fibre diets, all of which place added strain on bowel health. As a result, even people in their twenties and thirties should not ignore the risk and should start building awareness of colorectal cancer prevention early.

How to Recognise Early Colorectal Cancer Symptoms

The most dangerous aspect of colorectal cancer is that it may cause no symptoms at all in the early stage. Symptoms often only become noticeable when the tumour gradually grows larger. If you experience any of the following 8 common colorectal cancer symptoms on an ongoing basis,⁴ you should seek medical attention as soon as possible and consult a healthcare professional:

Changes in bowel habits, such as persistent constipation or diarrhoea, or alternating between both
Blood in the stool, including black stool or dark red blood
Occasional vomiting
A feeling of incomplete bowel emptying after passing stool
Abdominal discomfort, such as frequent pain, bloating or cramping
Unexplained weight loss
Symptoms of anaemia, such as persistent fatigue, pale complexion, shortness of breath, dizziness or rapid heartbeat
A hard lump in the abdomen or noticeable abdominal swelling

Many people assume that seeing blood in the stool is simply caused by haemorrhoids, which may delay diagnosis. Bleeding from haemorrhoids is usually bright red and often appears on the surface of the stool or drips after passing stool, and is commonly accompanied by pain. In contrast, bleeding caused by colorectal cancer is more often dark red, mixed with the stool, and usually painless in the early stage. However, it is difficult to make an accurate judgment based on appearance alone.¹⁴ If you notice any form of rectal bleeding, the safest approach is to seek a professional medical examination.

Understanding the Risk Factors for Colorectal Cancer

Modifiable Lifestyle and Dietary Factors⁵

Most cases of colorectal cancer are not caused by a single factor, but are closely linked to long-term unhealthy lifestyle habits:

Lack of exercise and obesity: Long-term physical inactivity and being overweight can increase cancer risk.
Smoking and excessive alcohol consumption: Carcinogens in tobacco and excessive alcohol intake may damage bowel cells.
High intake of red and processed meat: Frequent consumption of fatty red meat and processed meat cooked at high temperatures may raise the risk.

Non-Modifiable Family History and Personal Medical Conditions⁵

Some individuals have a higher risk of colorectal cancer due to inherited genetic factors or pre-existing medical conditions:

Family history: A close relative, such as a parent or sibling, has had colorectal cancer
Familial Adenomatous Polyposis (FAP): A condition in which a large number of polyps develop in the bowel, with a very high risk of becoming cancerous
Lynch Syndrome: A hereditary genetic mutation associated with increased risk of several cancers
Chronic inflammatory bowel disease: Such as ulcerative colitis or Crohn's disease

Building Your First Line of Defence Through Daily Habits: Colorectal Cancer Prevention Tips⁶

Developing healthy eating habits is the first line of defence in colorectal cancer prevention. In general, it is recommended to increase your intake of whole grains, beans, vegetables and fruits in your daily diet. A fibre-rich diet helps promote bowel movement and reduces the amount of time carcinogens stay in the intestines.

At the same time, you may consider reducing your intake of red meat and processed meat, such as sausages, bacon and ham. The International Agency for Research on Cancer (IARC), under the World Health Organization, has classified processed meat as carcinogenic to humans. Research suggests that consuming 50 grams of processed meat per day may increase the risk of colorectal cancer by around 18%. For better health, you may consider replacing processed meat and red meat with healthier white meat options such as chicken or fish, and choosing lower-temperature cooking methods such as steaming or boiling.⁷

In addition to dietary changes, regular exercise is equally important. According to the Department of Health guidelines,⁶ adults are advised to accumulate at least 150 minutes of moderate-intensity aerobic physical activity each week. Avoiding smoking and alcohol is also recommended.

Common Colorectal Cancer Screening Methods in Hong Kong⁸

Because early-stage colorectal cancer can be difficult to detect, regular screening is one of the best ways to identify and remove precancerous lesions, such as colorectal polyps, at an early stage.

Non-Invasive Screening: Faecal Occult Blood Test (FOBT)

The faecal occult blood test is a simple, non-invasive screening method that detects tiny amounts of blood in the stool that cannot be seen by the naked eye. To encourage early detection and colorectal cancer prevention, the Hong Kong Government has launched the Colorectal Cancer Screening Programme, which subsidises asymptomatic Hong Kong residents aged 50 to 75 to undergo faecal occult blood testing in the private sector.⁹ If the result is positive, further examination is required.

There are two main types of faecal occult blood tests: the guaiac faecal occult blood test (gFOBT) and the faecal immunochemical test (FIT). The former requires dietary restrictions to improve accuracy, while the latter does not.

Screening comparison⁸	gFOBT	FIT
Sample characteristics	Reacts to substances beyond human blood	Reacts only to human blood
Medication restrictions	Required to improve accuracy	Not required
Dietary restrictions	Required to avoid food interference	Not required
Number of samples	3	1-2
Interpretation of results	Based on colour change and may lead to errors	Uses standardised instruments and is generally considered more accurate

Colonoscopy and CT Colonography

According to the Department of Health, colonoscopy is currently the best method for examining the lower digestive tract. The procedure usually takes about 15 to 60 minutes. Before the examination, the patient must take laxatives to cleanse the bowel and follow a low-residue diet. A low-residue diet means eating foods that leave minimal undigested waste after digestion, helping prevent stool from remaining in the bowel and interfering with the colonoscopy procedure.¹⁰

If a doctor determines that a patient is not suitable for colonoscopy, CT colonography may be used as an alternative. This involves CT scanning to produce images of the inner wall of the colon, helping identify polyps or tumours.¹¹

Planning Ahead for Critical Illness and Medical Protection

If colorectal cancer is diagnosed at an early stage and treated promptly, the 5-year survival rate for stage 1 disease can exceed 90%.¹² Today, treatment options such as minimally invasive surgery, targeted therapy and immunotherapy can significantly improve both survival rates and quality of life.

However, both treatment costs and long-term support during recovery can involve considerable medical expenses. For example, undergoing a colonoscopy and polypectomy in a private medical institution may already cost around HK$10,000 to HK$30,000 for a single procedure,¹³ not to mention the potentially much higher cost of subsequent cancer treatments.

To reduce the financial burden that unexpected medical expenses may place on your family, you may consider planning ahead with critical illness and medical protection plans. This can help ensure access to suitable medical and financial support when facing uncertain health risks.

Colorectal Cancer Prevention FAQs

Early-stage colorectal cancer usually has no obvious symptoms. By the time symptoms such as blood in the stool or abdominal pain appear, the disease may already be at a more advanced stage. That is why preventive screening is especially important even when no symptoms are present. In general, people at average risk are advised to begin regular colorectal cancer screening at age 50. Those with a family history or other high-risk factors, such as a history of bowel polyps, should consult a doctor about starting screening earlier.⁴

Haemorrhoids are swollen veins near the anus and are a benign condition. They do not develop into colorectal cancer. However, both conditions can cause rectal bleeding and may easily be confused. Bleeding from haemorrhoids is usually bright red and painful, whereas bleeding caused by colorectal cancer is more often dark red and painless.¹⁵If you notice any suspicious symptoms, you should seek professional medical advice. This can also help clarify your health condition and avoid unnecessary underwriting concerns when planning future medical coverage.

If colorectal cancer is detected at stage 1 and treated appropriately, the 5-year survival rate can exceed 90%.¹² This clearly highlights the importance of regular screening and early diagnosis. At the same time, planning medical protection early while you are still young and healthy may help avoid future limitations in coverage caused by symptoms or existing medical history, such as bowel polyps, giving you more treatment options when facing health challenges.

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