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Anal Cancer: Tests After Diagnosis

What tests might I have after being diagnosed?

After a diagnosis of anal cancer, you’ll likely need more tests. These help your healthcare providers learn more about the cancer. They can help show if it has grown into nearby tissues or spread to other parts of your body. The test results help your providers decide the best ways to treat the cancer. If you have any questions about these or other tests, talk with your healthcare team.

The tests you need might include:

  • Transrectal ultrasound

  • CT scan

  • MRI

  • Chest X-ray

  • Positron emission tomography (PET) scan

Imaging tests

Transrectal ultrasound

Ultrasound uses sound waves to look inside your body. The waves are sent out from a wand-like probe that's put into your rectum. The sound waves bounce off your insides and send back signals, like sonar on a submarine. A computer then receives the signals and makes an image of the inside of your body.

This test can help healthcare providers find out if the cancer has spread deep into the tissues around the anus or to nearby lymph nodes in your pelvis. It can also show how big the tumor is and how deep the cancer has grown into the wall of the anus.

CT scan

For this test, you lie on a narrow table that moves through a ring-like CT scanner. It takes many X-rays as you slide through. A computer combines these images to make detailed pictures of your insides. You'll need to drink a special X-ray dye (contrast medium) just before the scan. Dye may also be put right into your blood through a vein in your arm or hand. The dye helps get clearer images.

This test can help show if the anal cancer has spread into your lymph nodes, liver, or other nearby organs. A CT scan is sometimes used to help guide the needle when doing a biopsy. A biopsy is when a tiny piece of tissue is taken out to check it for cancer cells.


MRIs use radio waves and magnets to make detailed pictures that look like slices of the body. You lie on a narrow table that slides through the long, narrow, tube-like scanner. Some people have trouble with this test because they don't like being in tight spaces. Let your healthcare provider know if this is a problem for you. You may be given medicine to help you do the test. A contrast dye will be put into a vein on your hand or arm before this test. This helps get better pictures.

MRIs can help your healthcare provider figure out where the tumor is and how big it is. They can also show if it’s spread to nearby tissues. For instance, MRI can show enlarged lymph nodes. This may be a sign that cancer has spread to them.

Chest X-ray

You may have an X-ray done to see if the cancer has spread to your lungs. Many times, a CT scan of the chest is used instead.

Positron emission tomography (PET) scan

A PET scan shows tissues actively using sugar (glucose). Quickly dividing cells, like cancer cells, use up more of the glucose. For this test, a small amount of radioactive glucose is put in your blood through a vein in your arm or hand. Then you lie still on a table that moves through the ring-like PET scanner. It rotates around you, looking for the radioactivity. It takes a picture of your whole body that shows "hot spots" where a lot of radioactivity was found.

PET scans don't show a lot of detail, so they're often done along with a CT scan. This is called a PET/CT scan. The combination gives detailed pictures of where cancer may be anywhere in your body.

Working with your healthcare provider

Your healthcare provider will talk with you about which tests you should have, how the test is done, and why you need it. Make sure to get ready for the tests as instructed. Ask questions and talk about any concerns you have.


Online Medical Reviewer: Jessica Gotwals RN BSN MPH
Online Medical Reviewer: Raymond Turley Jr PA-C
Online Medical Reviewer: Todd Gersten MD
Date Last Reviewed: 4/1/2023
© 2024 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.
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