Characteristics and Risk Factors of Interval Colorectal Advanced Adenomas after Negative Index Colonoscopy

Objectives Interval colorectal advanced adenoma (I-CRAA) carries insidious risk of interval colorectal cancer (I-CRC). The study aims to determine the frequency of I-CRAA after negative colonoscopy and discover the characteristics and the risk factors.Methods We retrospectively analyzed the information of the patients undergoing colonoscopy in the endoscopic center (2015-2019). Frequency of I-CRAA was calculated. The clinical features of I-CRAA were compared with sporadic colorectal advanced adenoma (Sp-CRAA). Results The frequency of I-CRAA was 0.71% (112/15759) per colonoscopy. I-CRAA was more likely to be located in the proximal colon (65.2% vs 34.8%, p<0.05) and has high pathological grade (5.4% vs 1.6%, p<0.05). Diabetes, family history of CRC, smoking, alcohol intake and diverticulosis are risk factors for I-CRAA（p<0.05）. Excellent bowel preparation (OR 3.727; 95% CI 2.425–5.73, p<0.001) and higher adenoma detection rate (OR 1.924; 95% CI 1.153–3.21, p = 0.012) are helpful for the detection of I-CRAA. I-CRAA found within 1 year other than 2 or 3 years after the initial colonoscopy were usually found by an endoscopist with higher ADR.Conclusions I-CRAA is usually located in the proximal colon and has high pathological grade. Diabetes, diverticulosis, smoking history, alcohol intake, and family history of CRC are the risk factors. Its occurrence is more related to low-quality colonoscopy, especially within one year.