When you first see your GP they will ask about your symptoms and whether you have a family history of bowel cancer.
They will then carry out a physical examination known as a digital rectal examination (DRE). A DRE involves your GP gently placing their finger into your anus, and then up into your rectum.
A DRE is a useful way of checking whether there is a noticeable lump inside your rectum. This is found in an estimated 40-80% of cases of rectal cancer.
A DRE is not painful, but some people may find it a little embarrassing.
If your symptoms suggest you may have bowel cancer, or the diagnosis is uncertain, you will be referred to your local hospital for further examination.
Further examination
Two tests are commonly used to confirm a diagnosis of bowel cancer:
- A sigmoidoscopy is an examination of your rectum and some of your large bowel.
- A colonoscopy is an examination of all of your large bowel.
Sigmoidoscopy
A sigmoidoscopy uses a device called a sigmoidoscope, which is a thin, flexible tube attached to a small camera and light.
The sigmoidoscope is inserted into your rectum and then up into your bowel. The camera relays images to a monitor. This allows the doctor to check for any abnormal areas within the rectum or bowel that could be the result of cancer.
A sigmoidoscopy can also be used to remove small samples of suspected cancerous tissue so they can be tested in the lab. This is known as a biopsy.
A sigmoidoscopy is not usually painful, but can feel uncomfortable. Most people go home after the examination has been completed.
Colonoscopy
A colonoscopy is similar to a sigmoidoscopy except a longer tube, called a colonoscope, is used to examine your entire bowel.
Your bowel needs to be empty when a colonoscopy is performed, so you will be given a special diet to eat for a few days before the examination and a laxative (medication to help empty your bowel) on the morning of the examination.
You will be given a sedative to help you relax, after which the doctor will insert the colonoscope into your rectum and move it along the length of your large bowel. As with a sigmoidoscope, the colonoscope can be used to obtain a biopsy, as well as relaying images of any abnormal areas.
A colonoscopy usually takes about one hour to complete, and most people can go home once they have recovered from the effects of the sedative. After the procedure, you will probably feel drowsy for a while, so arrange for someone to accompany you home.
Want to know more?
- Beating Bowel Cancer: Diagnosis
- Cancer Research UK: Bowel cancer tests
- Macmillan: Colonoscopy
Further testing
If a diagnosis of bowel cancer is confirmed, further testing is usually carried out for two reasons:
- to check if the cancer has spread from the bowel to other parts of the body
- to help decide on the most effective treatment for you
These tests can include:
- a computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan to provide a detailed image of your bowel and other organs
- ultrasound scans, which can be used to look inside other organs, such as your liver, to see if the cancer has spread there
- chest X-rays, which can be used to assess the state of your heart and lungs
- blood tests to detect a special protein, known as a tumour marker, released by the cancerous cells in some cases of bowel cancer
Staging and grading
Once the above examinations and tests have been completed, it should be possible to determine the stage and grade of your cancer. Staging refers to how far your cancer has advanced. Grading relates to how aggressive and likely to spread your cancer is.
- Stage 1 – the cancer is still contained within the lining of the bowel or rectum
- Stage 2 – the cancer has spread into the layer of muscle surrounding the bowel
- Stage 3 – the cancer has spread into nearby lymph nodes
- Stage 4 – the cancer has spread into another part of the body, such as the liver
This is a simplified guide. Stage 2 is divided into further categories called A and B and stage 3 is divided into A, B and C.
There are three grades of bowel cancer:
- Grade 1 is a cancer that grows slowly and has a low chance of spreading beyond the bowel
- Grade 2 is a cancer that grows moderately and has a medium chance of spreading beyond the bowel
- Grade 3 is a cancer that grows rapidly and has a high chance of spreading beyond the bowel
If you are not sure what stage or grade of cancer you have, ask your doctor.
Want to know more?
- Macmillan: Staging and grading of colon and rectal cancer
Diagnosing bowel cancer
