Doctors use a variety of tests to confirm a rectal cancer diagnosis and determine how far it has spread. These results help guide treatment decisions.
- Digital Rectal Exam (DRE): The doctor checks the rectum with a gloved finger to feel for abnormal growths.
- Colonoscopy: A colonoscopy is a test doctors use to look inside the rectum and colon for signs of cancer. It uses a long, bendable tube with a light and camera to take a close look at the lining of the colon. If anything unusual is found, such as a polyp, the doctor can remove it or take a small tissue sample (biopsy) during the same test.
- Biopsy: A small sample of tissue is examined under a microscope to confirm the presence of cancer cells.
- A barium enema is a special X-ray test used to look at the colon and rectum. It helps doctors see the lining, shape, and size of the lower part of the digestive system. During the test, a substance called barium is put into the large intestine to make it show up clearly on the X-ray. Sometimes, air is added to improve the image even more—this is called a double contrast study. The test often includes fluoroscopy, a type of live X-ray that shows the organs in motion. This helps doctors find any problems that might not show up on a regular X-ray.
- A sigmoidoscopy is a test that helps doctors look at the lower part of the colon, close to the rectum and anus. It’s often used to check for signs of rectal cancer. During the test, a thin, flexible tube with a light and camera is gently placed into the rectum to show a clear view of the area. Sometimes, air is added to help open the space for better visibility. This test can also be used to take a tissue sample or remove small growths like polyps.
- CT Scan (Chest, Abdomen, Pelvis): Imaging test to check if cancer has spread to organs like the liver or lungs.
- MRI of the Pelvis: Provides detailed images of the rectum and surrounding tissues, including nearby lymph nodes.
- Blood Tests:
- Complete Blood Count (CBC): Checks red and white blood cells. Low red blood cells may suggest blood loss.
- Comprehensive Metabolic Panel (CMP): Measures chemicals in the blood to assess kidney and liver function.
- Liver Enzyme Test: Detects possible cancer spread to the liver.
- Measures carcinoembryonic antigen (CEA), a protein that may be elevated in people with rectal cancer.
- Fecal Occult Blood Test (FOBT) or Fecal Immunochemical Test (FIT): This test checks for hidden blood in your stool. If blood is found, your doctor may recommend further testing.
Stages
Doctors use stages to describe how far the cancer has grown or spread. The higher the stage, the more advanced the cancer is.
- Stage 0: Cancer is only on the surface lining of the rectum. It hasn’t grown deeper.
- Stage 1: Cancer has grown under the lining and may have reached the rectal wall.
- Stage 2: Cancer has spread into the rectal wall and possibly into nearby tissue.
- Stage 3: Cancer has reached nearby lymph nodes and tissues outside the rectum.
- Stage 4: Cancer has spread to distant organs, like the liver or lungs.
