What Exams Are Needed When Colon Cancer Is Suspected?
1. Blood Test for Carcinoembryonic Antigen (CEA) Blood tests to measure CEA levels. CEA concentration only rises in already-established cancer cases. Liver disease can also elevate CEA, leading to false positives or delayed diagnosis.
2. Faecal Occult Blood Test Detects hidden rectal bleeding (small amounts not visible to the naked eye). Requires collecting samples for 3 consecutive days — inconvenient for patients. Cannot determine if bleeding is from the colon or other causes (e.g., haemorrhoids, anal fissure).
3. Complete Blood Count Detects anaemia which may indicate chronic blood loss.
4. Endoscopic Examination (with Barium Enema) Allows direct visualisation of the colon lining. Key benefit: tissue samples (biopsy) can be taken for confirmation, and polyps can be removed during the same procedure.
Comparison of Six Examination Methods
CEA Blood Test
Principle: Blood test to measure carcinoembryonic antigen (CEA) concentration.
⚠️ Limitation: Cannot detect polyps. Liver disease can cause elevated CEA, leading to false positives.
Virtual Colonoscopy
Principle: CT scan to visualise the interior of the colon. Accuracy exceeds 90%.
⚠️ Limitation: If abnormalities are seen, tissue biopsy is not possible. Full colonoscopy required for confirmation.
Painless Colonoscopy
Principle: A flexible endoscope is advanced through the entire colon, allowing direct observation and biopsy.
✅ Advantage: The most flexible examination method. If abnormalities are seen, biopsies can be taken immediately. Generally no limitations apply.
Barium X-Ray Enema
Principle: Barium (an X-ray-opaque substance) is inserted into the rectum, then an abdominal X-ray is taken to visualise polyps or tumours.
⚠️ Limitation: Cannot take tissue biopsies. Abnormalities require follow-up colonoscopy.
Pill Camera
Principle: The patient swallows a pill-sized camera that transmits images of the digestive tract to a receiver worn around the waist.
⚠️ Limitation: Cannot take tissue biopsies. If abnormalities are detected, a full colonoscopy is still required.
Faecal Occult Blood Test
Principle: Detects hidden rectal bleeding not visible to the naked eye.
⚠️ Limitation: Cannot determine the source of bleeding (haemorrhoids, fissure, etc.). Requires 3 consecutive days of samples — inconvenient.