Precancerous Lesions and Large Bowel Polyps

Written by A/Prof Viraj Kariyawasam, Gastroenterologist

1. What are Precancerous Lesions and Large Polyps?

Precancerous lesions and bowel polyps are abnormal growths that develop on the lining of the large bowel (colon or rectum). Most bowel cancers develop from these lesions over time, which is why their early detection and removal is so important.

Polyps vary in size and type. While many polyps are small and benign, some larger polyps or certain types of lesions have a higher risk of progressing to bowel cancer if left untreated.

2. Causes & Risk Factors

The exact cause of polyp formation is not always clear, but risk increases with age and certain lifestyle and genetic factors.

Risk factors include increasing age, family history of bowel polyps or bowel cancer, inflammatory bowel disease, smoking, excess alcohol intake, obesity, physical inactivity, and diets low in fibre and high in processed foods.

3. Symptoms & How They May Present

Most precancerous lesions and bowel polyps do not cause symptoms, particularly in the early stages.

When symptoms do occur, they may include rectal bleeding, iron deficiency anaemia, changes in bowel habits, or abdominal discomfort. Because symptoms are often absent, screening and surveillance are critical.

4. How Are They Diagnosed?

Precancerous lesions and polyps are most commonly detected during colonoscopy, either as part of bowel cancer screening or investigation of symptoms.

Advanced imaging techniques during colonoscopy allow careful assessment of polyp size, shape, and surface features. Biopsies may be taken to determine histology and cancer risk.

5. Treatment & Management Options

Most polyps and precancerous lesions can be removed endoscopically during colonoscopy, avoiding the need for surgery.

Large or complex polyps may require advanced endoscopic techniques such as endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD). These procedures allow safe and effective removal of lesions that previously required surgery.

6. Living With / Managing Precancerous Lesions

After removal of precancerous lesions, ongoing surveillance is important to detect any new polyps early.

Follow-up colonoscopy intervals are based on polyp size, number, and histology. Adopting healthy lifestyle measures can reduce the risk of future polyp formation.

7. Prevention & Risk Reduction

Regular bowel cancer screening and surveillance colonoscopy are the most effective ways to prevent bowel cancer.

Maintaining a healthy diet rich in fibre, regular physical activity, limiting alcohol intake, and avoiding smoking all contribute to lower risk.

8. When to Seek Medical Advice

You should seek medical advice if you have rectal bleeding, unexplained iron deficiency, persistent bowel habit changes, or a family history of bowel cancer or polyps.

If you have been diagnosed with a large or complex polyp, specialist assessment is important to determine the safest and most effective treatment approach.