Further tests after diagnosis

You will have tests to find out the size and position of the cancer, and whether it has spread. This is called staging. It will help you and your doctor make decisions about your treatment.

Your blood may be tested for a protein called carcinoembryonic antigen (CEA). If the level of CEA is high, your doctors will check it regularly to see how well your treatment is working.

You will have a CT scan, which uses x-rays to see whether the cancer has spread outside the rectum. You will also have an MRI scan. This uses a magnet to build up a picture of the inside of your body. Some people may have an endorectal ultrasound, which uses sound waves to show the cancer in the rectum. Or you may have a PET/CT scan, which uses low-dose radiation to identify areas of cancer.

It may take up to two weeks for all your test results to be ready. This can be a stressful time. You may find it helpful to talk about your worries with someone close to you.

Further tests

If any of your biopsies show that there is cancer in the bowel, you will have more tests. These are to find out the size and position of the cancer and whether it has spread. This is called staging.

The results will help you and your doctor decide on the best treatment for you. Some tests may be repeated during and after treatment to check your progress. Your doctor or specialist nurse will explain this to you.

The tests you have may include:

  • blood tests to assess your general health
  • a CT scan to check for any signs that the cancer has spread outside the bowel
  • a PET/CT scan if more detailed information is needed or if there is cancer in the liver or lungs
  • an MRI scan is done to plan surgery and if there is cancer in the liver.


Blood tests

Your blood may be tested for a protein called carcinoembryonic antigen (CEA). Some people with bowel cancer have higher levels of this protein. If your level of CEA is high, your doctors may check it regularly to see how well your treatment is working.


What happens in a CT scan?

A CT scan takes a series of x-rays, which build up a three-dimensional picture of the inside of the body. The scan takes 10–30 minutes and is painless. It uses a small amount of radiation, which is very unlikely to harm you and will not harm anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan.

CT scan
CT scan

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You may be given a drink or injection of a dye, which allows particular areas to be seen more clearly. This may make you feel hot all over for a few minutes. It’s important to let your doctor know if you are allergic to iodine or have asthma, because you could have a more serious reaction to the injection.

You’ll probably be able to go home as soon as the scan is over.


MRI scan

This scan uses magnetism to build up a detailed picture of areas of your body. You may be given an injection of dye, into a vein, to improve the images from the scan. This test is painless and will take around 30 minutes. We have more detailed information about having an MRI scan.


Other tests

The following tests are sometimes used. You can discuss with your doctor whether they are appropriate for you.


Endorectal ultrasound scan (ERUS)

This test may be used to help plan your operation. Ultrasound scans use sound waves to build up a picture of body tissues. An endorectal ultrasound scan can show the size and location of a cancer in the rectum.

For the test, you lie on your left side with your knees bent up. A nurse or doctor gently passes a small, lubricated probe into the back passage. This produces an image of the rectum on a screen.

The scan takes about 10 minutes and you can usually go home as soon as it’s over.


PET/CT scan

This is a combination of a CT scan (see above) and a positron emission tomography (PET) scan. A PET scan uses low-dose radiation to measure the activity of cells in different parts of the body.

A PET/CT scan may occasionally be done if more detailed information is needed after a CT scan. It may also be used to help the doctors plan treatment if there is cancer in the liver or lungs.

You won’t be able to eat for six hours before the scan, although you may be able to drink. A technician injects a small amount of mildly radioactive glucose (sugar) into a vein in your hand or arm. The radiation dose is very small. You then wait for the glucose to be absorbed by your body. After an hour or so you have the scan, which takes 30–90 minutes. The scan will show areas where the glucose has been absorbed. Cancers absorb more glucose than other parts of the body. This helps the doctors identify any areas of cancer. You can usually go home after the scan.


Waiting for test results

Waiting for test results can be a difficult time. It may take from a few days to a couple of weeks for the results of your tests to be ready. You may find it helpful to talk with your partner, family or a close friend. Your specialist nurse or one of the organisations listed on our database, can also provide support. You can also talk things over with one of our cancer support specialists on 0808 808 00 00.

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