Medical history and physical exam. Your doctor will take your medical history, and will ask about any symptoms, including when they started and how long you’ve had them. As part of a physical exam, your doctor will feel your abdomen for masses or enlarged organs, and also examine the rest of your body. You may also have a digital rectal exam (DRE). During this test, the doctor inserts a lubricated, gloved finger into your rectum to feel for any abnormal areas.
Tests to look for blood in your stool. Your doctor may recommend a test to check your stool for blood that isn’t visible to the naked eye, called occult blood. You would do this at home, either a fecal occult blood test (FOBT) or fecal immunochemical test (FIT).
Blood tests. Your doctor might also order certain blood tests to be used to help monitor your disease if you’ve been diagnosed with cancer.
Complete blood count (CBC). This test measures the different types of cells in your blood, and it can show if you have anemia.
Liver enzymes. You may also have a blood test to check your liver function, because colorectal cancer can spread to the liver.
Tumor markers. Blood tests for these tumor markers can sometimes suggest someone might have colorectal cancer, but they can’t be used alone to screen for or diagnose cancer.
Diagnostic colonoscopy. Your doctor looks at the entire length of your colon and rectum with a colonoscope, a thin, flexible, lighted tube with a small video camera on the end. Special instruments can be passed through the colonoscope to biopsy or remove any suspicious-looking areas such as polyps.
Proctoscope. May be done if rectal cancer is suspected. Your doctor looks inside the rectum with a proctoscope, a thin, rigid, lighted tube with a small video camera on the end. The tumor can be seen, measured, and its exact location can be determined.
Biopsy. The definitive step in a proper diagnosis. Your doctor removes a small piece of tissue with a special instrument passed through a scope. A pathologist examines the biopsy samples under a microscope, and if cancer is found, other lab tests may also be done on the biopsy specimens to help better classify the cancer.
Imaging tests use sound waves, x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Possible tests include:
- Computed tomography (CT or CAT) scan. Helps us see if colon cancer has spread into your liver or other organs.
- Abdominal ultrasound. Can be used to look for tumors in your liver, gallbladder, pancreas, or elsewhere in your abdomen, but it can’t look for tumors of the colon.
- Endorectal ultrasound. Used to see how far through the rectal wall a cancer has grown and whether it has reached nearby organs or tissues such as lymph nodes.
- Intraoperative ultrasound. Done during surgery, allowing the surgeon to biopsy the tumor while the patient is asleep.
- Magnetic resonance imaging (MRI) scan. Can be used to look at abnormal areas in the liver or the brain and spinal cord that could be cancer spread.
- Endorectal MRI. MRI scans can be used in patients with rectal cancers to see if the tumor has spread into nearby structures.
- Positron emission tomography (PET) scan. If you have already been diagnosed with cancer, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body. Some machines can do both a PET and CT scan at the same time.
- Angiography. An x-ray test for looking at blood vessels.
- Chest x-ray. May be done after colorectal cancer has been diagnosed to see if cancer has spread to the lungs.