Bowel polyps

Also called colon polyps

Bowel polyps are growths that develop on the wall of the large intestine or rectum. They are not usually cancerous but they need to be removed when discovered as some will eventually turn into cancer.

What are bowel polyps?

Polyps are growths that develop in your large intestine (bowel or colon) or the rectum (anus or bottom). They are usually less than 1 cm in size, although they can grow up to several centimetres. Bowel polyps are caused by abnormal production of cells in the bowel wall.

There are different forms of polyps – some are a tiny raised area or bulge, some look like a grape on a stalk and others take the form of many tiny bumps clustered together. Some people just develop one polyp, while others may have a few. 

Bowel polyps are not usually cancerous but, if left untreated, some will eventually turn into cancer and need to be removed once discovered.

Read more about the different types of polyps and the risk of getting bowel cancer.

Who is at risk of getting bowel polyps?

Bowel polyps can develop in anyone, but they are more common in people aged over 50 years. Polyps can run in families, so you may be more likely to develop polyps if a family member has them. People with a family history of bowel cancer are also more likely to develop polyps. 

You may also have a greater chance of developing polyps if you:  

What are the symptoms of bowel polyps?

Most people with polyps are not aware they have them, as polyps don't usually produce symptoms. They are often discovered by accident. Some larger polyps can cause:

  • a small amount of rectal bleeding (blood in your poos)
  • mucus (slime) to be produced when you open your bowels
  • a change in your bowel habits, either diarrhoea (runny poos) or constipation
  • tummy pain.

How are polyps diagnosed?

Bowel polyps are usually found as a result of a bowel investigation for conditions like inflammatory bowel disease or bowel cancer. These investigations are done via a sigmoidoscopy, which checks the last part of your bowel, or a colonoscopy, which checks the whole length of your large bowel. Any polyps found are removed during the procedure and sent away to the laboratory for testing. If the polyps are found during a sigmoidoscopy, a colonoscopy is needed to check the whole of your large bowel for polyps.

How are bowel polyps treated?

Bowel polyps are usually removed, even if they do not cause any symptoms. This helps to reduce the risk of getting bowel cancer. Bowel polyps can be removed during a colonoscopy.

  • During the procedure, the doctor passes a long wire loop through a colonoscope (a long, soft flexible tube containing a tiny video camera and a light) and around the base of the polyp. The loop is pulled tight, cutting off the polyp.
  • An operation (surgery) is rarely needed to remove polyps but may be necessary if the polyps are very large or can't be reached safely during the colonoscopy.
  • After removal, the polyp is sent to a laboratory to check for any signs of cancer. 

Some people will need further colonoscopies because polyps can recur.

  • Polyps can sometimes run in families. This is uncommon but means you'll need colonoscopy checks at regular intervals.
  • You might be asked to have repeat examinations around every 3 to 5 years to catch any further polyps that may develop and potentially turn into bowel cancer.

Learn more

The following links provide further information on bowel polyps. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Bowel polyps NHS Choices, UK, 2017
Bowel polyps Patient Info, UK, 2016 
Bowel cancer – information for people at increased risk of bowel cancer New Zealand Guidelines Group, 2012
Familial Adenomatous Polyposis (FAP) New Zealand Familial GI Cancer Service 

References

  1. Guidance on surveillance for people at increased risk of colorectal cancer New Zealand Guidelines Group, 2012