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EMR of large (≥2 cm) nonpedunculated colorectal polyps (LNPCPs) is associated with high rates of recurrent/residual adenoma, possibly because of microadenoma left at the margin of resection. Data supporting this mechanism are required. We aimed to determine the incidence of residual microadenoma at the defect margin and base after EMR. We performed a retrospective observational study of patients undergoing EMR of large LNPCPs with the lateral defect margin further resected using the EndoRotor device (Interscope Medical, Inc, Worcester, Mass, USA) after confirming no visible residual adenomatous tissue. Aspects of the defect base were also resected in selected patients. Patients underwent surveillance at 3 to 6 months. Resection of the normal defect margin was performed in 41 patients and of aspects of the base in 21 patients. Mean lesion size was 43.0 mm (range, 20-130). Microscopic residual lesion was detected in the margin of apparently normal mucosa in 8 cases (19%). In 7 cases this was an adenoma, and in 1 case a serrated lesion was found at the margin of a resected tubular adenoma. Microscopic residual lesion was detected at the base in 5 of 21 cases. Residual/recurrent adenoma was detected in 2 patients. Neither had residual microadenoma at the lateral margin or base detected after the primary resection. Microscopic residual adenoma after wide-field EMR was detected in 19% of cases at the apparently normal defect margin and at the resection base in 5 of 21 cases. This study confirms the presence of residual microadenoma after resection of LNPCPs, providing evidence for the mechanism of recurrence. [ABSTRACT FROM AUTHOR]

Purpose: Almost any colorectal superficial neoplastic lesion can be treated by endoscopic resection (ER) but very little is known about outcomes of ER leaving circumferential or near-circumferential mucosal defects. We report the outcomes of ER leaving ≥ 75% circumferential mucosal defects performed in a western expert centre. Methods: Five hundred eighty-seven ERs of large colorectal lesions ≥ 20 mm were grouped according to the extent of the mucosal defect and comparisons made between those with < 75% and ≥ 75% defects. Independent predictors of stenosis were identified. Results: Forty-seven patients had ER leaving ≥ 75% circumference defect, most located at or distal to the rectosigmoid, with ≥ 90% defects in 5 and 100% in 11. There were no significant colonic muscle injuries in patients with ≥ 75% defect and no differences in post-procedure bleeding (OR 1.6, 95% CI 0.2–13.7, p = 0.64) between patients with ≥ 75% and < 75% defects. Stenosis developed in 9 patients. ≥ 90% circumference defect was the only independent risk factor for stenosis (OR 286, p < 0.001). Three of 4 patients with asymptomatic stenosis had successful expectant management. The remainder were treated with dilatation. Recurrence was more likely in those with ≥ 75% defect (OR 7.9, 95% CI 3.8–16.4, p < 0.001) but was managed with further ER in all but 2 cases. Conclusion: ER of colorectal lesions resulting in defects ≥ 75% of the luminal circumference is challenging but safe and effective when performed in an expert centre. The only independent predictor of stenosis is ≥ 90% circumference defect but some patients improve with expectant management; therefore, pre-emptive intervention may not be warranted. [ABSTRACT FROM AUTHOR]