Effect of Diminutive Adenoma with High-Grade Dysplasia on Surveillance Colonoscopy Interval

Background: Colonoscopy surveillance guidelines set the surveillance schedule based on polyp characteristics. Polyps with high-grade dysplasia (HGD) require 3 years of follow-up regardless of size. However, it is unclear whether patients with diminutive polyps (<= 5 mm) with HGD have a higher risk. We evaluated the effect of diminutive adenoma with HGD on adenoma occurrence. Methods: From January 2015 to December 2017, patients who underwent index and surveillance colonoscopy were retrospectively screened. The patients were grouped into no adenoma group, low-risk (patients with <= 2 low-grade dysplasia [LGD]), diminutive HGD, and high-risk (HGD >5 mm, >= 3 adenomas) groups according to the index colonoscopy results. Each group was analyzed using logistic analysis. Results: The mean follow-up period was 22.47 months. Altogether, 610 (50.45%) patients had LGD and 152 (12.5%) had HGD. Among them, 61 (5.0%) patients had a diminutive polyp with HGD. Analysis of the risks of developing advanced adenoma in the surveillance colonoscopy showed that compared to the no adenoma group, the diminutive HGD group did not show a significant risk (odds ratio [OR] = 1.503 [0.449-5.027], p = 0.509), while the high-risk group showed a significant risk (OR = 2.044 [1.015-4.114], p = 0.045). Conclusions: Diminutive adenoma with HGD increased the risk of adenoma on surveillance colonoscopy, and in the case of advanced adenoma, the risk was increased, but it was not statistically significant.