Hi there! Thank you for your question. Colorectal cancer is the most important gastrointestinal malignancy. There are 3 locations where colorectal cancer can occur :
1. Right sided cancer - usually present with asymptomatically or anaemia symptoms due to chronic low grade bleeding
2. Left sided cancer - usually present with constipation, rectal bleeding, colicky or dull aching pain.
3. Rectal cancer – presents with early morning diarrhea, pain, feeling of incomplete defecation (tenesmus) or bleeding at the end of defecation.

If these symptoms are present and colorectal cancer is suspected, several investigations can be done such colonoscopy (gold standard and most commonly done), double contrast barium enema (if colonoscopy can’t be done), rectal ultrasound, ultrasound of abdomen (to check for spread of tumour), CT scan of chest and abdomen (to check for spread of tumour) and chest X-ray (to check for spread of tumour).

Screening test are done in patients about 50 with no symptoms or for patients with high risk. For asymptomatic patient above 50, the screen test use is faecal occult blood test (testing for the presence of microscopic or invisible blood in the stool, or feces). The idea of using faecal occult blood testing as a screening test is because colonic neoplasms such as early-stage cancer and large adenomatous polyps will bleed. The faecal occult blood test most commonly used is the Hemoccult II test.

CEA (blood marker for colon cancer) levels are not recommended in the asymptomatic individuals as a screening method. For high-risk patients (strong family history - two or more relatives with colon cancer or relatives who have had cancer at ages younger than 40) with no symptoms, digital rectal examination and faecal occult blood testing should be done as early as age 35 yearly.

Total colonoscopy or contrast barium enema and sigmoidoscopy should be performed at age 40 and then repeated every three to five years with yearly faecal occult blood tests. FOBT can be done at any government/private hospital or even at selected clinics.

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