Colonic polyps are mucosal lesions that project into the lumen of the large bowel. Most colonic polyps cause no symptoms, but they may cause rectal bleeding, mucus in stools, abdominal pain and, rarely, diarrhoea or constipation. There is a significant risk that, after several years, polyps may develop into bowel cancer if left untreated.
Benign polyps and those with very early signs of malignancy can often be successfully removed by endoscopic polypectomy, or endoscopic mucosal or submucosal resection. However, polyps that are non-lifting usually involve deeper layers of the bowel wall because of either invasion by malignant cells or scarring from previous attempts at removal. Trying to remove these polyps by standard techniques risks incomplete resection of invasive disease and bowel perforation.