Tests after a diagnosis of colon or rectal cancer
If the biopsy shows that there is cancer in the colon or rectum, further tests will be done to find out the size and position of the cancer, and to see whether it has spread.
This process is called staging, and it may take some time. We have more information about detailed staging of bowel cancer.
The results will help you and your doctor decide on the best treatment for you. Sometimes these tests may be done again, during and after treatment, to check on your progress. Your doctor or specialist nurse will discuss with you which tests will be appropriate for you.
The following additional tests are most often used with bowel cancer:
You will probably have blood tests to assess your general health. Your blood may be tested for a protein called carcinoembryonic antigen (CEA), which is sometimes higher in people with bowel cancer.
These are often taken to check the health of your heart and lungs.
CT (computerised tomography) scan
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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.
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.
The following tests are sometimes used. You can discuss with your doctor whether they are appropriate for you:
PET (positron emission tomography) scan
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PET scans can be used to accurately define the cancer and find out if it has spread to other parts of the body.
A PET scan uses low-dose radioactive glucose (a type of sugar) to measure the activity of cells in different parts of the body. A very small amount of the mildly radioactive substance is injected into a vein, usually in your arm. A scan is then taken a couple of hours later. Tumours normally absorb more of the glucose and the radioactivity shows up on the scan. PET scans aren’t available in all hospitals, and you may have to travel to a hospital some distance away to have one.
This is a combination of a CT scan, which takes a series of x-rays to build up a three-dimensional picture, and a positron emission tomography (PET) scan, which uses low-dose radiation to measure the activity of cells in different parts of the body (see above). PET/CT scans give more detailed information about the part of the body being scanned. It is a new type of scan, so you may have to travel to a specialist centre to have one.
You won’t be able to eat for six hours before the scan, although you may be able to drink. A mildly radioactive substance is injected into a vein, usually in your arm.
The radiation dose used is very small. The scan is done after at least an hour’s wait, and usually takes 30-90 minutes.
You should be able to go home after the scan.
MRI (magnetic resonance imaging) scan
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An MRI is used mainly to help with the staging of rectal cancer.
This test uses magnetism to build up a detailed picture of areas of your body. The scanner is a powerful magnet, so you may be asked to complete and sign a checklist to make sure it’s safe for you. The checklist asks about any metal implants you may have, such as a pacemaker, surgical clips or bone pins.
You should also tell your doctor if you’ve ever worked with metal or in the metal industry, as very tiny fragments of metal can sometimes lodge in the body. If you do have any metal in your body, it’s likely that you won’t be able to have an MRI scan. In this situation another type of scan can be used.
Before the scan, you’ll be asked to remove any metal belongings including jewellery. Some people are given an injection of dye into a vein in the arm, which doesn’t usually cause discomfort. This is called a contrast medium and can help the images from the scan to show up more clearly.
During the test, you’ll lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It’s painless but can be slightly uncomfortable, and some people feel a bit claustrophobic. It’s also noisy, but you’ll be given earplugs or headphones. You can hear, and speak to, the person operating the scanner.
This is a special x-ray of the bowel that is only done occasionally. It will be done in the hospital x-ray department. It’s important that the bowel is empty so that a clear picture can be seen.
Your doctor or nurse will give you an instruction sheet before the test as there are some things you’ll need to do in preparation. On the day before the test, you’ll be asked to drink plenty of fluids and to take medicine (a laxative) to empty your bowel. On the morning of your enema, you usually shouldn’t have anything to eat or drink. This may vary slightly from hospital to hospital.
Just before the test, you may be given a bowel wash-out to make sure that your bowel is completely clear. The nurse will ask you to lie on your left side while a tube is gently passed into your back passage. Water is then passed through the tube. You will be asked to hold the liquid in the bowel for a few minutes before going to the toilet.
For the barium enema, a mixture of barium (a white, liquid substance that shows up on x-rays) and air is passed into the back passage. This is done in the same way as the bowel wash-out and may feel uncomfortable. You will be asked to keep the mixture in the bowel until all the x-rays have been taken. The doctor can then watch the passage of the barium through the bowel on an x-ray screen. Any lumps or swellings will show up.
The test can be uncomfortable and tiring, so it’s a good idea to arrange for someone to travel home with you, if possible.
For a couple of days after your enema, you may notice that your stools are white. This is the barium leaving the body and is nothing to worry about. The barium can also cause constipation, and you may need to take a mild laxative for a couple of days after your test.
Abdominal ultrasound scan
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Some people may have an ultrasound. This uses sound waves to look at internal organs, such as the liver and the inside of the abdomen, to see whether the cancer has spread to other organs. You will usually be asked not to eat or drink for at least six hours before the test. Once you are lying comfortably on your back, a gel is spread onto your abdomen. A small device that produces sound waves is passed over the area. The sound waves are then converted into a picture by a computer. The test only takes a few minutes.
In some situations, you may have a probe (like a tube) inserted into the rectum to produce ultrasound scans. This is known as an endoscopic ultrasound (EUS).
Waiting for your test results
It will probably take several days to a couple of weeks for the results of your tests to be ready. The results of the tests will show the grade and the stage of the cancer. This information will be used by a team of doctors and nurses, known as the multidisciplinary team or MDT, to decide on the most appropriate treatment.
Waiting for results can be a difficult time. It may help to talk things over with a friend or relative. You can also contact one of our cancer support specialists or one of the organisations listed in the further resources section.