What are polyps?

Polyps are small growths of the inner lining of the colon or rectum (bowel). They may be a little bulge on the surface (sessile) or on a stalk (pedunculated). They are common, affecting 15-20% of the adult population. The vast majority of polyps are quite harmless but some polyps have the potential to become a cancer.  Fortunately, the process of change to become a cancer usually takes many years and most polyps never turn malignant.  Nevertheless, because of the potential to become cancerous, polyps require removal.  In this way, it is hoped to prevent bowel cancer formation.

Polyps come in three main types

  • Adenomas – these are benign tumours
  • Hyperplastic – these are not tumours and have no real significance
  • Malignant – occasionally an adenoma can have some cancerous elements inside it


Most polyps produce no symptoms at all because of their small size.  Larger polyps may cause bleeding, mucous discharge or alteration in bowel function.


Polyps are often found when investigating the bowel because of bleeding or altered bowel habit. Sometimes they are the cause of the symptoms but more commonly they are incidental findings. Bigger polyps are sometime discovered on a CT scan or a PET scan. They can only really be diagnosed accurately by direct visualisation – essentially this means a colonoscopy.


Almost all polyps can be removed at colonoscopy. The polyp can be cauterised or snared with a wire using electric current; this does not hurt.  The polyp is then sent for analysis to determine its character. Larger polyps occasionally need more than one treatment for complete removal and a few require an operation. Removal of polyps with the colonoscope does carry a tiny risk of perforation or bleeding; this is a smaller risk than leaving the polyp.


If your polyp is of a certain size or type you may be at risk of developing further polyps in the future. Thus you may need to have repeat examinations at intervals of 1-5 years and you will be entered into a surveillance program. The aim of surveillance is to prevent cancer, and it is usually very effective. Nevertheless, no cancer prevention program can be 100% and so if you have symptoms that concern you, such as bleeding or change in bowel function, then you should contact your doctor in the usual way.