If your GP thinks you have symptoms that could be caused by a colorectal cancer, they will refer you to see a specialist colorectal consultant.

Investigations and diagnosis

Patients may be referred for a number of investigations and scans in order to find out whether they have a colorectal cancer. These investigations also allow doctors to make a diagnosis and see the extent of any disease.

Diagnostic investigations may include:

  • Proctoscopy/ Sigmoidoscopy – a flexible, lighted tube is put into the rectum and lower colon to check for polyps and cancer
  • Colonoscopy – a long, flexible tube is used to look at the entire colon and rectum
  • Barium Enema – a test that helps highlight the bowel, so it can be clearly seen on an X-ray. A white liquid is passed into your bowel through your bottom.
  • CT – uses X-rays and a computer to create detailed images of the inside of the body
  • CT colonography – a CT scanner is used to produce detailed pictures of the colon and rectum
  • MRI – a type of scan that uses strong magnetic fields and radio waves to produce detailed images of the inside of the body
  • PET – a scan used to produce detailed three-dimensional images of the inside of the body

Staging and grading of colorectal cancer

Your colorectal cancer specialist needs certain information about the cancer to decide on the most appropriate treatment for you. This includes the stage and grade of the cancer. The stage of a cancer describes its size, position and whether it has spread to beyond the area of the body where it started.

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


Your investigation results will be discussed at the colorectal cancer multidisciplinary meeting. 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.