Diagnosis

Tests to diagnose rectal cancer

Rectal cancer can be found during a screening test for colorectal cancer. Or it may be suspected based on your symptoms. Tests and procedures used to confirm the diagnosis include:

• Using a scope to examine the inside of your colon and rectum (colonoscopy). Colonoscopy uses a long, flexible tube (colonoscope) attached to a video camera and monitor to view your colon and rectum. If cancer is found in your rectum, your doctor may recommend examining your colon in order to look for additional suspicious areas.

• Removing a sample of tissue for testing (biopsy). If any suspicious areas are found, your doctor can pass surgical tools through the colonoscope to take tissue samples (biopsies) for analysis and remove polyps.

  The tissue sample is sent to a lab to be examined by doctors who specialize in analyzing blood and body tissues (pathologists). Tests can determine whether the cells are cancer, whether they're aggressive and which genes in the cancer cells are abnormal. Your doctor uses this information to understand your prognosis and determine your treatment options.

Tests to look for rectal cancer spread

Once you're diagnosed with rectal cancer, the next step is to determine the cancer's extent (stage). The stage of your cancer helps determine your prognosis and your treatment options.

Staging tests include:

• Complete blood count (CBC). This test reports the numbers of different types of cells in your blood. A CBC shows whether your red blood cell count is low (anemia), which suggests that a tumor is causing blood loss. A high level of white blood cells is a sign of infection, which is a risk if a rectal tumor grows through the wall of the rectum.
• Blood tests to measure organ function. A chemistry panel is a blood test to measures levels of different chemicals in the blood. Abnormal levels of some of these chemicals may suggest that cancer has spread to the liver. High levels of other chemicals may indicate problems with other organs, such as the kidneys.
• Carcinoembryonic antigen (CEA). Cancers sometimes produce substances called tumor markers that can be detected in blood. One such marker, carcinoembryonic antigen (CEA), may be higher than usual in people with colorectal cancer. CEA testing is particularly useful in monitoring your response to treatment.
• CT scan of the chest. This imaging test helps determine whether rectal cancer has spread to other organs, such as the liver and lungs.
• MRI of the pelvis. An MRI provides a detailed image of the muscles, organs and other tissues surrounding a tumor in the rectum. An MRI also shows the lymph nodes near the rectum and different layers of tissue in the rectal wall.

Your doctor uses information from these tests to assign your cancer a stage. The stages of rectal cancer are indicated by Roman numerals that range from 0 to IV. The lowest stage indicates cancer that is limited to the lining of the inside of the rectum. By stage IV, the cancer is considered advanced and has spread (metastasized) to other areas of the body.