Aim  Colonoscopy to detect and remove polyps has contributed to a reduction in colorectal carcinoma. Three‐year follow up is recommended for patients considered to be at high risk (at least three adenomas, adenoma ≥ 1 cm, villous or high‐grade features). Our study focused on patients diagnosed with high‐grade dysplasia with regard to initial management and follow up. Method  A search of patients who had had endoscopic removal of a high‐grade adenoma was carried out. Patients with the following were excluded: follow up of < 1 year, polyposis syndromes, prior colon cancer and a diagnosis of adenocarcinoma within 6 months following initial diagnosis. Results  Eighty‐three patients treated between 1999 and 2007 for high‐grade dysplasia (HGD) in a colorectal adenoma were identified. Over a median follow‐up period of 4 years, 53 (64%) developed further adenomatous polyps. Among these, 7% had an adenoma with HGD or an adenocarcinoma. In all these patients, the initial high‐grade adenoma was > 1 cm in diameter. Initial follow‐up colonoscopy was performed on average 7 months following the initial diagnosis. Ten per cent of patients underwent prophylactic segmental resection, and 6% received argon laser therapy. Conclusion  The study demonstrates that patients who have a colorectal adenoma > 1 cm with HGD may be at high risk of developing further adenomas with HGD or carcinoma. Close follow up is warranted.

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