Bowel polyps affect between 15 and 20% of the UK population. Polyps are small growths on the inner lining of the large bowel (colon) that vary in size, shape and speed of growth.
A polyp’s shape is described as flat or pedunculated (on a stalk). Assessment in the laboratory provides more information. The most common type are called ‘adenomas’ and over time these can develop into cancer. The rate of polyp growth is difficult to predict; the other less common slower growing type are called ‘hyperplastic’ polyps. Testing in the laboratory identifies if there are cancerous changes, this is uncommon when the polyps are smaller than 1cm.
For this reason, polyps will usually be removed if they are detected during a colonoscopy.
Bowel polyps are more common in people aged over 60.
Bowel polyps don’t normally cause symptoms so people often don’t realise they have them. If they grow to a larger size, they may cause looser stool, rectal bleeding or mucous.
As many as a third of bowel cancers may be caused by a fault in one or more of our genes passed down through families (inherited). Less than 10% of bowel cancers have a specific identified genetic abnormality evident from birth, examples include:
People with this condition develop a large number of polyps in the lining of the bowel and have a very high chance of developing bowel cancer.
Most people with FAP have surgery to remove the colon and sometimes the rectum as well to prevent them from developing bowel cancer, regular endoscopy is also recommended. FAP is uncommon, with less than one in 100 bowel cancers (1%) being caused by the condition. It is associated with other cancers including small bowel and connective tissue. The different clinical types are determined by different mutations in the FAP gene
This is similar to FAP with multiple polyps and a lifetime risk of developing bowel cancer of more than 90%. To develop MAP you must inherit not one but two copies of the faulty gene, one from each of your parents (autosomal recessive).
- causes one in every 30 bowel cancers (3.3 per cent). In addition to bowel cancer it increases the risk of several other types of cancer, including cancer of the urinary tract, female reproductive organs and stomach.
- If you or your family has HNPCC, you will be offered regular colonoscopies from the age of 25 to check for polyps, which can be removed before they develop into cancer.
- If you have 3 relatives with bowel cancer or 2 relatives with any of the associated cancers and 1 under 45 years of age, it is possible you have the HNPCC gene abnormality in your family and should discuss the role of regular colonoscopies with a specialist.
- NICE and the Royal College of Pathologists recommend that younger patients with bowel cancer have the tumour checked for HNPCC type genetic faults.
- Being over the age of 50
- Type 2 diabetes
- Having an unhealthy lifestyle
- Longstanding inflammatory bowel diseases such as Crohn’s or ulcerative colitis
- A history of polyps in your bowel.
Polyps are detected on, colonoscopy (endoscopic camera examination of the whole of the bowel), sigmoidoscopy (examination of the last part of the bowel) or with a special CT scan called a CT colonography.
Screening can detect a polyp or cancer before any symptoms have developed and when there is the greatest chance of successful treatment.
Bowel cancer screening is offered to all NHS patients in England and Wales from the age of 60 (50 in Scotland). This involves having a stool test to identify patients that may be at risk and then a colonoscopy. However, people who have a family history of bowel polyps or cancer are advised to have a colonoscopy from the age of 50 or younger for a strong family history or for added peace of mind.
Other risk factors include:
- Getting older – 90% of bowel cancers occur in people over the age of 50
- Previous diagnosis of cancer or polyps – if you have previously had cancerous polyps or bowel cancer, the chances of recurrence are higher. You will automatically be called for regular screening using colonoscopies to check for further polyps
- Certain lifestyle choices increase your risk of developing bowel cancer, including: smoking, drinking alcohol, obesity, lack of exercise and eating a diet high in red or processed meat.
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