If your GP thinks you have symptoms that could be caused by a colorectal cancer, they will refer you to see a specialist doctor in the hospital. This doctor will work with a range of specialist healthcare professionals and will discuss your case with them, to ensure the best treatment plan for you.

Investigations and diagnosis

Patients may be referred for a number of investigations and scans in order to find out if they have a colorectal cancer. These investigations also allow the specialist team to make a diagnosis.

Diagnostic investigations may include:

  • Colonoscopy / flexible sigmoidoscopy – a long, flexible camera is used to look at the colon and rectum. Biopsies can be taken and polyps can be removed during the procedure.
  • CT scan – a series of x-rays are taken to build up a three-dimensional picture of inside the body. The CT scan produces detailed images of many structures inside the body, including internal organs, bones and blood vessels. CT stands for Computer Tomography.
  • CT Colonography (CTC) – a test which uses CT scans to produce detailed images of the large bowel and rectum. It is also called a virtual colonoscopy.
  • MRI – a type of scan that uses strong magnetic fields to produce detailed images of soft tissue (flesh) inside the body. MRI stands for Magnetic Resonance Imaging.
  • PET scan – this scan uses a mildly radioactive drug to show up any areas of the body where cells are more active than normal. It can help to find out if and where the cancer has spread. PET stands for Positron Emission Tomography, and is only done in the Royal Group of Hospitals in Belfast.

Staging of colorectal cancer

Your specialist team needs certain information about the cancer to decide on the most appropriate treatment for you. This includes the stage of the cancer, which describes its size and whether it has spread anywhere else in the body.

The TNM system is the most commonly used staging system.

T – describes how far the tumour has grown into the wall of the bowel, and whether it has grown into nearby tissue or other organs.
N – describes whether the cancer has spread to the lymph nodes.
M – describes whether the cancer has spread to another part of the body such as the liver or lungs (metastatic or secondary cancer).

For more information on the staging and grading of each colorectal cancer, visit the Macmillan Cancer Support website.


The results of your tests, scans and investigations will be discussed at the colorectal cancer Multi Disciplinary Team (MDT) meeting. The MDT is a well established group of specialists comprising of doctors, nurses, radiographers and other healthcare professionals who manage the treatment of colorectal cancers. The team will review all aspects of your care and recommend an appropriate treatment plan. A member of the team will discuss this with you.

Share this page

Email Icon Print Icon

Investors In People