Diagnosis of colorectal cancer
A suspicion of colorectal cancer typically arises during a doctor’s appointment based on the symptoms reported by the patient. To detect colorectal cancer and confirm the diagnosis, physicians have various methods at their disposal. The choice of diagnostic methods and the extent to which they are carried out directly influence the clarity of the diagnosis.
Summary
The diagnosis of colorectal cancer (colon or rectal cancer) is based on several examinations:
-
Stool test (fecal occult blood test): Used to check for hidden (occult) blood in the stool.
-
Colonoscopy: An endoscopic examination where the bowel is examined using a camera, allowing for tissue samples to be taken.
-
Sigmoidoscopy: An endoscopic examination focusing on the lower part of the large intestine.
-
Imaging studies (e.g., CT or MRI scans): Performed to evaluate the extent and spread of the cancer.
-
Biopsy (tissue sample): Confirms the diagnosis through microscopic examination.
A definitive diagnosis can only be confirmed based on a biopsy taken during a colonoscopy.
How is colorectal cancer diagnosed?
Digital rectal examination (DRE)
When colon or rectal cancer is suspected, the lower part of the rectum is usually examined first. The doctor performs this by inserting a gloved finger into the rectum through the anus to feel for any unusual lumps and to check for any potential blood in the stool.
Colonoscopy
When a colon tumor is suspected, a colonoscopy (an endoscopic examination of the large intestine) is the primary diagnostic test. A flexible endoscope, or colonoscope, allows for the examination of the entire large intestine, from the rectum all the way to the beginning of the small intestine. If any abnormalities are detected during the procedure, the doctor will take a biopsy (tissue sample) for analysis and/or remove polyps (small growths on the mucous membrane). These procedures are typically painless for the patient. However, the carbon dioxide introduced into the bowel to improve visibility, along with the stretching caused by the scope, may cause some discomfort. If requested, premedication (sedation or pain relief) can be provided before the procedure to help ease anxiety or discomfort.
A successful colonoscopy requires thorough bowel cleansing (bowel preparation), and you will receive instructions for this from the clinic performing the examination.
For many, a colonoscopy raises questions and sometimes anxiety. We have put together a four-part lecture series to help you understand what the examination involves, how to prepare for it, and what happens during the procedure.
Lecture series on colonoscopy (available in Finnish)Colorectal cancer screening
The purpose of colorectal cancer screening is to detect colorectal cancer at an early stage, when it is more likely to be curable.