How is Colon Cancer Diagnosed?


Colon Cancer Diagnosis

Once someone is suspected to have colon cancer based on signs and symptoms, further investigations are needed to confirm the diagnosis and stage the disease. Some diagnostic techniques can accurately determine the extent of cancer invasion in the intestinal wall and spread of the disease to other body parts, which in turn help in selecting an appropriate treatment option.

colon cancer staging investigations

Digital Rectal Examination

digital rectal examination

  • Digital rectal examination can be done in which a doctor examines the rectum for an abnormality by inserting a lubricated, gloved finger via the anus.
  • This test can provide little information about cancer within the rectum or in nearby organs. Thus, detailed investigations are required to establish the diagnosis of cancer.

Barium Enema/Double-Contrast Barium Enema (DCBE)

double contrast barium enema

  • In double contrast barium enema, a thick, viscous liquid containing barium (a heavy element that reflects x-rays) and the air is administered into the rectum and colon via the anus.
  • Then, x-rays images are obtained for the lower abdomen where any polyps or cancer lesions are detected by the irregular barium coating.
  • The test has relatively higher sensitivity for larger lesions and in symptomatic patients. It cannot be used to determine the extent of invasion or the spread of cancer to distant organs.


colonoscopy for colon cancer  

  • Colonoscopy is a diagnostic technique which uses a colonoscope that enables to directly observe the lining of the rectum and entire colon to look for any abnormality and collect biopsy.
  • Colonoscopy is one of the most important investigations which is required to confirm the disease. In this, a colonoscope is passed through the rectum into the intestine, that helps in localising the site of the tumor. We can take a biopsy from the tumor for histopathological diagnosis.

colonoscopy diagram

  • Also we can do an endoscopic ultrasound, to assess the depth of infiltration of tumor and involvement of adjacent structures and regional lymph nodes by the tumor.

Flexible sigmoidoscopy

flexible sigmoidoscopy

  • This technique is very similar to with the only difference being the extent of the area examined during the test.
  • Sigmoidoscopy helps in examining the distal part of the colon and the complete rectum.

Carcinoembryonic antigen (CEA)

  • An elevated level of serum CEA may be associated with colorectal cancer, but it may be false positive or false negative in some cases.
  • This can, however, be useful in assessing the efficacy of the treatment/surgery and the progression/recurrence of the disease.
  • CEA is the tumor marker for colon cancer. Baseline level of CEA should be done to assess the response to treatment.

Laboratory and Imaging

  • Biopsy samples contains a small piece of tissue, collected from the colonic mass with the help of a biopsy instrument.
  • Imaging tests help in staging of the disease. CT scan of abdomen helps us to assess the local and distant spread of the tumor to other structures. Rarely, PET CT scan may also be required. Imaging of chest with X-ray or CT scan may also be required in some cases, depending upon the symptoms.


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