Colorectal Cancer Diagnosis

If you are being examined for colorectal cancer, the first thing your doctor will do is review your medical history. He or she will conduct a thorough medical exam. Your doctor may conduct one or more of the following tests.

Digital Rectal Exam

Why it is done: This is to check the rectum for lumps or abnormalities. About half of colon cancers can be detected in this way.

What to expect: The doctor will insert a lubricated, gloved finger into the rectum. A rectal exam is particularly helpful if a test for occult blood is conducted at the same time.

Fecal Occult Blood Test

Why it is done: Blood in stool (bowel movement) can indicate colorectal cancer. It’s sometimes hidden, or not visible to the naked eye. Stool may contain blood for many reasons. It does not always mean colorectal cancer.

What to expect: In this procedure, a small sample of stool is placed on a chemically treated card. A laboratory then tests it for hidden blood. If there is blood found in the stool sample, a more specialized test like colonoscopy may be necessary.

X-ray of the Large Intestine or Barium Enema

Why it is done: An X-ray provides a picture of the colon. This helps the doctor identify any polyps.

What to expect: Often this is done by inserting a liquid called barium into the colon through a rectal tube. This is an uncomfortable procedure, but not painful. It takes about an hour. The barium provides contrast so polyps show up better on the X-ray.

Colonoscopy Procedure

Why it is done: Colonoscopy is used to examine the bowel’s interior surface for abnormalities like polyps.

What to expect: In this procedure, the doctor inserts a flexible tube into the bowel. The tube contains a camera. The colonoscopy lets the doctor examine the inside of the entire colon and rectum. If the doctor discovers a polyp or abnormal tissue, it may be removed and sent for further testing. Removal of a polyp is called polypectomy.


Why it is done: A biopsy allows the doctor to remove a tissue sample to then be sent to a pathologist for examination. This is to check if the tissue sample is benign or malignant.

Benign vs. Malignant: What’s the Difference? Benign means not cancerous. A benign tumor can get larger but does not spread to other tissues or organs.

Malignant means cancerous. A malignant tumor’s cells can invade nearby tissue and lymph nodes and then spread to other organs. These cells are destructive.

Benign tumors:

  • Can be removed
  • Usually don’t grow back
  • Are rarely fatal
  • Don’t spread to other tissues or body parts

Malignant tumors:

  • Can often be removed
  • Sometimes grow back
  • Can invade other tissues and organs and cause damage
  • Can spread to other body parts
  • Can be fatal

What to expect: The doctor will prescribe laxatives or an enema before the procedure, to cleanse the colon. In the procedure, the doctor will insert a colonoscope or sigmoidoscope. The doctor will anesthetize (numb) the area where the sample will be collected. This will minimize pain. There will probably be mild bleeding and discomfort after the procedure.

Virtual Colonoscopy

Why it is done: This is a type of CT scan. It uses computer software along with CT imaging to examine the colon for polyps.

What to expect: In this procedure, a rubber catheter is inserted to force air into the colon. Some of the benefits of a virtual colonoscopy are that it:

  • Does not require the insertion of tubes (as in colonoscopy).
    • Prevents the slight risk of possible injury to the bowel.
    • Does not require sedation.
      • Makes recovery time shorter.
      • Means the person having the procedure won’t need someone to drive them.

Virtual colonoscopy is not available everywhere. Some doctors feel it is almost as effective as endoscopy in identifying polyps. However, if a polyp is found by virtual colonoscopy, a second procedure will be needed to remove and examine it. With conventional endoscopy, the biopsy can usually be done at the same time.