Colonic Polyps and Bowel Cancer


 

Introduction

Bowel (colorectal) cancer is the third most common cancer in the UK and unfortunately the second most common cause of cancer related death.  Colonoscopy enables the detection of bowel cancer at an early stage often before symptoms develop. Thereby, improving the chance of recovery and improving survival. As most bowel cancer is thought to arise from polyps, colonoscopy can also help prevent bowel cancer by removing these polyps when they are found.  Colonic polyps are small benign (noncancerous) growths on the inside of the lining of the colon or rectum. If identified at colonoscopy they are removed since there is a small risk of a colonic polyps developing in to bowel cancer after many years.

Types of colonic polyps

Colonic polyps are common findings; approximately 20% of people having a colonoscopy will have a polyp identified in the colon. About 1 in 4 people over the age of 50 develop at least one colonic polyp. Usually polyps less than 1cm are always benign, however, polyps greater than 1 cm have a higher risk of becoming cancerous over many years.  Polyps often do not cause any symptoms, however larger polyps may cause visible bleeding or invisible bleeding leading to anaemia. Sometimes polyps can cause a change in bowel habit.

Removal of polyps at colonoscopy is called polypectomy. The polyp is then sent to the laboratory for analysis under the microscope.

Adenomas are polyps that have the potential to develop cancer. Approximately one quarter of adenomas will turn malignant over many years. If one does turn cancerous the change takes place over a number of years. Most colorectal cancers develop from a polyp that has been present for 5-15 years.

Hyperplastic polyps are commonly found in the rectum. There are usually small and almost always benign. These small polyps can be left alone although commonly are removed or biopsied.
Inflammatory or pseudopolyps – are caused by chronic inflammation for example inflammatory bowel disease. These do not need to be removed.

Who should have a colonoscopy

There are groups of patients who are at increased risk of bowel cancer and colonoscopy is recommended for surveillance in these patients.

  1. A family history of bowel cancer
  2. A personal history of colonic polyps or bowel cancer
  3. Inflammatory bowel disease

Patients with certain symptoms or signs should also consider a colonoscopy

  1. A change in bowel habit
  2. Iron deficiency anaemia of unknown cause
  3. Rectal bleeding
  4. Chronic diarrhoea