How is colorectal cancer diagnosed and assessed?

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Initial assessment

If a doctor suspects that you may have colorectal cancer, he or she will examine you to look for signs such as a lump in your abdomen, anaemia, etc. The examination will usually include a rectal examination. This is where a doctor inserts a gloved finger through your anus into your rectum to feel if there is a tumour in the lower part of the rectum. However, often the examination is normal, especially if the cancer is in it's early stages. Therefore, one or more of the following tests may be arranged.

A faecal occult blood test (FOB test). A small sample of faeces is smeared onto a piece of card. A simple test can detect small amounts of blood in your faeces which you would not normally see or be aware of. Occult means 'unseen' or 'invisible'. The FOB test can only say that you are bleeding from somewhere in the gut. It cannot tell from which part. Nor can it tell what is causing the bleeding. It is a useful test to confirm 'bleeding' within the gut. However, other tests are needed to confirm the cause of the bleeding which may be colorectal cancer or some other condition.
Colonoscopy. A colonoscope is a thin, flexible, telescope about as thick as a finger. It is passed through the anus and into the colon. It can be pushed all the way round the colon to where the small and large intestine meet. The colonoscope contains fibre optic channels which allows light to shine down so the operator can see inside your colon.
Flexible sigmoidoscopy. This is similar to colonoscopy. The difference is that a shorter telescope is used which is pushed only into the rectum and sigmoid colon.
Barium enema. This is an x-ray test to obtain pictures of your colon and rectum. The colon and rectum do not show up very well on ordinary x-ray pictures. However, if barium liquid is placed in the colon and rectum, their outline shows up clearly on x-ray pictures. This test is done much less more commonly thesedays since colonoscopy has become available.