Colorectal Cancer Diagnosis

If your doctor finds something suspicious during a screening exam, or if you have symptoms of colorectal cancer, your doctor may perform one or more diagnostic tests to pinpoint the cause.

Medical History Review and Physical Exam

Your gastroenterologist will conduct a thorough review of your personal and family medical history to identify hereditary or genetic risk factors. He or she will also perform a deeper inquiry into your specific symptoms and examine your abdomen, rectum or other areas as needed.

Blood & Screening Stool Tests

Blood tests may be required to check the levels of several key substances in your blood. Shield by Guardant Health is an FDA-approved blood test to screen for colorectal cancer.

Screening stool (feces) tests include:

• High-sensitivity fecal occult blood test (FOBT) – This test checks for hidden blood (small amounts of blood not detectable by visual inspection) in three consecutive stool samples.
• Fecal immunochemical test (FIT) – This test checks for occult (hidden) blood in the stool and is sometimes preferred over FOBT.
• Cologuard – This test checks for occult blood in the stool and altered DNA, which can cause colon cancer or polyps. For this at-home test you collect your stool, place it in the provided container and mail it to the lab. 

Endoscopic Procedures

Endoscopic procedures use flexible lighted tubes to examine your colon and rectum. The two main types of endoscopic procedures used to help diagnose colorectal cancer are colonoscopy and flexible sigmoidoscopy.

For a colonoscopy, your doctor uses a flexible, lighted tube (colonoscope) to examine the interior walls of your rectum and the entire colon. Colonoscopies can be used as screening tests or as follow-up diagnostic tools when the results of another screening test are positive.

For a flexible sigmoidoscopy, your doctor uses a flexible, lighted tube (sigmoidoscope) to look at the interior walls of your rectum and the sigmoid (the left side of the colon). 

Biopsy

A biopsy is a procedure  to remove cells or tissue for testing in order to determine whether or not a tumor is cancerous. An endoscopic biopsy is conducted during a colonoscopy or sigmoidoscopy. It is the most common biopsy used to diagnose colon and rectal cancer.

For colorectal cancer, a biopsy most often includes removal  of a sample of abnormal cells for your pathologist to examine. If your doctor sees something suspicious during a screening endoscopy, he or she will likely perform a biopsy as part of the examination.

Imaging Tests

Imaging tests are a helpful tool but cannot detect colon or rectal cancer alone. Your doctor may conduct one or more imaging tests such as ultrasound, X-ray, computed tomography (CT) scan or MRI to identify the location of the cancer and determine whether it has spread to other organs.

Ultrasound: An ultrasound is a type of imaging test that uses sound waves to visualize organs inside the body  and detect any abnormalities. 

Double-contrast barium enema: A double-contrast barium enema (or lower gastrointestinal or GI series) is an X-ray test that highlights the inner part of the colon and rectum.

Computed tomography (CT) scan: A CT scan is a type of imaging test that uses X-rays to create detailed cross-sectional pictures inside the body. A CT colonography (or virtual colonoscopy) creates a 3-D view of your colon and rectum.

Magnetic resonance imaging (MRI) scan: An MRI scan uses magnets and radio waves to provide cross-sectional images of the colon, rectum and nearby organs.