How colon cancer is diagnosed
Usually, the first thing you do it see your GP, who will examine you. You may have to have blood tests done to check the overall state of your health. If your GP is unsure of what the problem is or if they believe it may be cancer, they will send you to a hospital for specialist treatment and advice.
At the hospital, your specialist will ask you about your overall health and any previous medical problems of yours or family history of colon cancer. You will have examinations done, possibly including a rectal exam, blood tests, and a colonoscopy.
This can normally be done on an outpatient basis, lasting about one hour. Your intestines should be completely empty, which is why you will be given instructions on what to eat and drink the day before. Also, you may be given a laxative. You may be given an intravenous sedative to help you during the test.
You will have a flexible tube (colonoscope) inserted into your anus. The colonoscope contains a light and a small camera that can be used to photograph any abnormal areas in your intestines. Also, biopsies may be taken from these areas so that the samples can be sent to the laboratory to see if they contain any cancer cells.
- Virtual colonoscopy (CT colonography, CT enema)
A CT takes a series of x-rays, creating a 3-D image of the inside. This can be done instead of a colonoscopy or in cases where the colonoscopy does not provide a clear enough image.
Usually, this can be done on an outpatient basis. Your intestines should be completely empty, which is why you will be given instructions on what to eat and drink on the days before the procedure . Also, you may be given a laxative. You may be given an intravenous sedative to help you during the test.
Just before the CT scan, a tube is inserted into your anus to administer air and gas so as to expand the intestine and help produce a clearer image.
This test searches the inside of the rectum and the part of the colon that is closest to the rectum (sigmoid colon).
Usually, this is done on an outpatient basis. A flexible is inserted into the anus to administer a small amount of air so as to see the inside more clearly. During the test, tissue samples (biopsies) may be taken from any part of the colon that looks to be abnormal.
- Blood tests
Blood tests are done to assess your overall state of health. These analyses may measure the protein CEA, as levels of this protein are higher in some cases of colon cancer.
- CT (computed tomography)
This exam is done to detect any sign that the cancer has spread beyond the colon. In this test, a series of x-rays is taken, creating a 3-D image of the inside. It takes from 5 to 15 minutes and is painless.
A small amount of radiation is used, though it is very unlikely to cause you any harm. You will be asked to refrain from eating and drinking for at least four hours before the test.
You may be given a drink or an injection with a dye, which makes it possible to see certain areas more clearly. This may make you feel hot for a few minutes. It is important that you inform your health professionals if you are allergic to iodine or have asthma, as you may have a reaction to the injection.
CT scans can also be used as a guide during biopsies.
- PET / CT
This is a combination of computed tomography and positron emission tomography (PET). PET uses low doses of radiation to measure cell activity in different parts of the body. This test offers more detailed information on the part of the body being scanned.
You will not be able to eat for six hours before the test. A slightly radioactive substance is injected into a vein (normally the arm). This is followed by a wait of at least an hour before the examination, which takes between 30 and 90 minutes.
- MRI (magnetic resonance imaging)
This test uses magnetism to build a detailed image of one of the areas of your body. The scanner is a powerful magnet, which is why you will be asked to fill out and sign a checklist and provide your consent. As part of this consent form, you will be asked if you have any implants such as a pacemaker or surgical clips. You should also tell your doctor if you have ever worked with metals or in the metal industry.
Before the scan, you will be asked to remove all metal belongings, including jewelery. Sometimes, a contrast dye is given by injection in a vein of the arm to help the images come through more clearly.
You will have to remain very still during the test, which lasts about 30 minutes. The process is painless but can be somewhat uncomfortable, and some people experience a bit of claustrophobia. It is also quite loud, though you will be given earplugs or headphones.