What are the symptoms of colorectal cancer?
When a colorectal cancer first develops and is small it usually causes no symptoms. As it grows, the symptoms that develop can vary, depending on the site of the tumour. The most common symptoms to first develop are:
- Bleeding from the tumour. You may see blood mixed up with your faeces (stools or motions). Sometimes the blood can make the faeces turn a very dark colour. The bleeding is not usually severe and in many cases the bleeding is not noticed as it is just a small 'trickle' which is mixed with the faeces. However, small amounts of bleeding that occur regularly can lead to anaemia which can make you tired and pale.
- Passing mucus with the faeces.
- A change from your usual 'bowel habit'. This means you may pass faeces more or less often than usual.
- Bouts of diarrhoea or constipation.
- A feeling of not fully emptying the rectum after passing faeces.
- Abdominal pains.
As the tumour grows in the colon or rectum, symptoms may become worse and can include:
- The same symptoms as above, but more severe.
- You may feel generally unwell, tired, or lose weight.
- If the cancer becomes very large, it can cause a blockage (obstruction) of the colon. This causes severe abdominal pain and other symptoms such as vomiting.
- Sometimes the cancer makes a hole in the wall of the colon or rectum (perforation). If this occurs the faeces can leak into the abdomen. This causes severe pain.
If the cancer spreads to other parts of the body, various other symptoms can develop.
All the above symptoms can be due to other conditions, so tests are needed to confirm colorectal cancer.
How is colorectal cancer diagnosed and assessed?
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.
There are separate leaflets that describe each of the above tests in more detail.
Biopsy - to confirm the diagnosis
A biopsy is when a small sample of tissue is removed from a part of the body. The sample is then examined under the microscope to look for abnormal cells.
If you have a colonoscopy or sigmoidoscopy, the doctor or nurse can take a biopsy of any abnormal tissue. This is done by passing a thin grabbing instrument down a side channel of the colonoscope or sigmoidoscope.
Assessing the extent and spread
If you are confirmed to have colorectal cancer, further tests may be done to assess if it has spread. For example, a CT scan, an MRI scan, an ultrasound scan, or other tests. (There are separate leaflets which describe each of these tests in more detail.) This assessment is called 'staging' of the cancer. The aim of staging is to find out:
- How much the tumour in the colon or rectum has grown, and whether it has grown partially or fully through the wall of the colon or rectum.
- Whether the cancer has spread to local lymph nodes.
- Whether the cancer has spread to other areas of the body (metastasised).
By finding out the stage of the cancer it helps doctors to advise on the best treatment options. It also gives a reasonable indication of outlook (prognosis). For colorectal cancer, it may not be possible to give an accurate staging until after an operation to remove the tumour.医学全在线www.med126.com
A common staging system for colorectal cancer is called the Duke's classification. This is:
- Duke A: the cancer is just in the inner lining of the colon or rectum.
- Duke B: the cancer has grown to the muscle layer in the wall of the colon or rectum.
- Duke C: the cancer has spread to at least one lymph node near to the colon or rectum.
- Duke D: the cancer has spread to other parts of the body ('metastases' or secondary tumours). The most common sites for colorectal cancer to spread to are the liver and lungs.
Other classification systems are sometimes used. For example, the TMN classification system is being increasingly used. See separate leaflet called 'Cancer Staging and Grading' for more details.
What is the treatment for a bowel polyp?
If a polyp is found during a colonoscopy (or sigmoidoscopy) it can often be easily removed. This is done by using special fine instruments which are passed down side channels of the colonoscope. When the polyp is removed it is then looked at under the microscope.
- Most polyps do not contain cancer cells. However, removing the polyp prevents the risk that it may become cancerous sometime in the future.
- Some polyps contain cancer cells. If these cells are confined to within the polyp then the removal of the polyp is curative. If the cells look as if they had begun to spread to the wall of colon or rectum then an operation may be needed to remove that section of colon or rectum.
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