Medical history, family history and physical exam
If you have any symptoms of rectal cancer, your doctor will start by asking you questions about your medical and family history and completing a physical exam. Your physical exam may include a rectal exam with a gloved finger, where your doctor checks for any lumps that can be felt in the rectum.
During an endoscopic procedure, your care team uses a thin tube with a light and camera to get a closer look at the inside of your rectum. The two main endoscopy procedures used to diagnose rectal cancer are colonoscopy and sigmoidoscopy.
- Colonoscopy: A colonoscopy provides a view of the inside of the entire colon and rectum. It also allows your doctor to take samples of polyps or tissue in the rectum and send them to the lab to help with a diagnosis.
- Sigmoidoscopy: This endoscopic procedure is similar to a colonoscopy, but instead of viewing the entire colon, your care team only looks at the lower portion of the colon. A sigmoidoscopy also may require taking tissue samples for testing.
Stool tests look for signs of blood or DNA in your stool that might be a sign of colorectal cancer or polyps in the colon or rectum. Usually, these tests are completed from the comfort of your home, allowing you to collect stool samples when it’s convenient for you. If stool tests are positive, they’re usually followed by a colonoscopy.
- Guaiac-based fecal occult blood test (gFOBT): Fecal occult blood testing looks for blood in the stool and requires multiple samples to be sent to the lab. With this test, you may need to change your medications or diet.
- Fecal immunochemical test (FIT): A fecal immunochemical test is an at-home test to help detect blood in the stool. With this stool test, you’ll collect multiple samples, but you don’t have to change your diet or medications.
- DNA stool test: Along with checking for blood, a DNA stool test also checks for pieces of DNA in the stool that could be signs of rectal cancer.
If your care team finds rectal polyps or abnormal cells in the lining of the colon and rectum during a colonoscopy or sigmoidoscopy, they’ll take tissue samples for more testing, called a biopsy. These samples are examined closely under a microscope in the lab to look for pre-cancerous changes or cancerous cells.
Especially after an initial diagnosis of rectal cancer, your doctor may use several types of imaging tests to help determine your rectal cancer stage. These tests may provide more detailed images of your rectum or look for signs that rectal cancer has spread to other areas of the body.
- CT scan: As a screening for rectal cancer, CT imaging may be used during a CT colonoscopy, also known as a virtual colonoscopy. After a diagnosis, CT scans often help determine how much rectal cancer has spread or how well your treatment is working.
- MRI: After a rectal cancer diagnosis, you may have an MRI (magnetic resonance imaging) to help with rectal cancer staging. This test uses strong magnets and radio waves to create cross-section images of your body.
- PET/CT scan: This imaging test helps highlight cells in the body that might be cancerous. It’s often used to see if rectal cancer has spread to other places in the body or the lymph nodes, which helps decide the stage of the cancer.
- Chest X-ray: A chest X-ray lets your care team look for signs of rectal cancer spreading to the lungs.
- Angiography: During an angiography, your doctor injects dye into your arteries to provide images of your blood vessels. It’s often used to examine the blood vessels supplying blood to a tumor if bleeding heavily.
- Ultrasound: Ultrasounds create images using sound waves, which are used in several ways in rectal cancer. You may have an endorectal ultrasound that takes images inside the rectum or an abdominal ultrasound to look for signs of cancer spreading to other organs. Intraoperative ultrasound is when an ultrasound is used during surgery.
- Barium enema: A barium enema is a type of X-ray imaging test. During this imaging procedure, barium is inserted into the rectum to coat it and help provide a clear silhouette of the rectum and colon.