What is a polyp?
A polyp is a protrusion from the lining of the bowel, caused by an
abnormal multiplication of cells. It may be a local raised area, look like a grape with a
narrow stalk, or take the form of many fine projections, resembling the pile of a carpet.
Why are polyps important?
If not removed, some types of polyp may grow and eventually lead to
cancer. Removal of a polyp or polyps is a good way of reducing the risk of bowel cancer.
What are the symptoms of polyps?
Most polyps cause no symptoms. Sometimes they bleed easily and the blood
can be seen mixed with the stool or on its surface. A polyp may also secrete clear mucus
which is passed with the stool. Very rarely, a polyp can cause a partial or complete
blockage of the bowel which leads to unexpected constipation or diarrhoea with abdominal
pain, bloating and, in severe cases, vomiting.
What tests might be required to
make a diagnosis?
Polyps are usually found during two types of test. First, an endoscopy
which involves passing a flexible telescope up from the anus. A sigmoidoscope can examine
the lower bowel, a colonoscope is longer and can examine the whole of the large bowel. If
an abnormality is present, the operator will be able to see it and take a small piece of
tissue (biopsy) for testing. The other test used is an X-ray examination using barium to
outline the bowel (barium enema). To carry out a barium enema a small tube is placed in
the anus and barium and air are introduced. The barium will outline the bowel and X-rays
will be taken from different angles so that any irregularity in the bowel wall caused by a
polyp will be detected.
What treatments are available?
When polyps are detected, they can often be removed painlessly using a
colonoscope, though occasionally an operation is required. When using a colonoscope, a
wire ÔsnareÕ is manoeuvred around the base of the polyp, tightened, and the polyp is
separated from the bowel wall by passing a small electric current down the wire.
What happens after treatment?
After removal of a polyp, it will be examined by specialists using a
microscope. The microscopic appearance will help decide whether the polyp has been removed
completely and what risk there is of it coming back.
Follow up after polyp removal
There are 2 main types of polyps. There are some types of polyp which
are very unlikely to develop into cancer. If patients have a polyp of this type, often no
further treatment or follow up is necessary.
Secondly, there are polyps which do carry a risk of becoming cancerous
or are cancerous. This type of polyp is also called an ÒadenomaÓ. If an adenoma was
present and was fully removed at colonoscopy no further treatment is necessary. But even
after complete removal of an adenoma there is a risk of developing new adenomas. So
patients will be followed up and many doctors would recommend at least one check
colonoscopy after a few years.
Occasionally, the microscopic analysis of the polyp will suggest that
there is a risk that the polyp was not completely removed, or had cancerous cells within
it. A second colonoscopy or an operation may then be needed to try to ensure that the
abnormal tissue is removed completely.
Familial Polyps
There are uncommon inherited conditions, including Òfamilial
adenomatous polyposisÓ, in which people develop several or many polyps. In this
situation, special treatment, including surgery, may be required.
Research
Many laboratories around the world are investigating ways of treating
the genetic make-up of patients with polyps and a liability to bowel cancer. In addition,
screening, by endoscopy, large groups of people without any abnormal symptoms is being
tested to assess the feasibility and results of detecting and removing polyps amongst a
large section of the population.
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