Healthy Living

Diagnosing Colon Cancer

Diagnosing Colon Cancer

Key Takeaways

  • A colonoscopy is the gold standard investigation for diagnosing colon cancer.
  • Carcino Embryonic Antigen (CEA) is a good prognostic factor.
  • CT scan, chest X-ray, and Ultrasound scans can be used to assess the spread of the cancer.

Signs and symptoms of colon cancer are not specific, which makes it difficult to diagnose. Therefore, investigations are crucial to make a diagnosis of colon cancer.

The first time you visit your doctor, he or she will record a complete medical history, including a detailed family history to check if you have got any risk factors or any other problems with your colon. After taking a careful history, your doctor will do a physical exam where he or she will feel your abdomen and examine the rest of your body. Next, your doctor will carry out some routine tests to assess the general fitness of you. 

Tests for colon cancer include:

  • Complete blood count – A low hemoglobin level indicating that there has been a chronic bleeding leading to anemia.
  • Erythrocyte Sedimentation Rate (ESR) – ESR may be increased.
  • Stool full report to assess for occult blood in the stools.
  • Liver function tests
  • Renal function tests
  • Blood sugar levels
  • Cardiac echo and ECG.

None of the above mentioned investigations can ultimately determine if you have colon cancer or not but it is merely done to assess the overall health condition. Your doctor will also want to perform a colonoscopy, an ultrasound scan, and a CT scan.

  • Colonoscopy – This is the gold standard investigation. A colonoscopy uses a flexible tube which has a video camera attached to it. Using a colonoscope the inside of your rectum and colon can be viewed on the screen. A biopsy needle can also be sent through the tube to take a tissue sample.  Even though it is invasive and uncomfortable to the patient this is the only investigation which can give an accurate diagnosis. At the same time of colonoscopy, a biopsy can be taken for final confirmation.
  • An ultrasound scan – This is a simple baseline non-invasive test. It is not painful at all. This test uses high frequency sound waves to create an image of some part of your body. An ultrasound scan is able to pick up a colonic mass if present and can identify if the cancer has spread to the liver. In addition, it also gives a clue as to whether there is fluid build-up in the abdomen.
  • A CT scan – This is more objective and precise. It is able to provide good details about the structures in the body.

Once a diagnosis of colon cancer is made, your doctor will suggest you to do some more additional tests to find out how much the cancer has spread. Your doctor will then continue to do a chest X-ray, a carcino embryonic antigen, and another CT scan.

  • Chest X-ray – To look for secondaries in the lungs. Colonic carcinoma spreads more often to the lungs. These are known as cannon ball secondaries.
  • Carcino Embryonic Antigen (CEA) – Carcino Embryonic Antigen is a surface glycoprotein produced by the colorectal epithelium. If the CEA levels have grossly increased in the follow up period of colorectal carcinoma, it suggests that the cancer has spread and is now in an advanced stage. The Carcino Embryonic Antigen levels give a good idea about the prognosis of the disease and therefore will be measured time to time. It also gives a clue whether the cancer is responding to the treatment.
  • CT scan – CT scan is a baseline investigation done to mainly to detect the spread of the disease. A contrast enhanced CT scan is the best in detecting small metastasis to the liver.