Using a standard endoscope (PCF-Q260AI, PCF-Q260AZI, PCF-PQ260; Olympus, Tokyo, Japan), CS was performed by 5 expert endoscopists, each of whom had performed more than 2,000 colonoscopies. A polyethylene glycol preparation was used as bowel cleansing agent. Depending on the severity, flexible sigmoidoscopy was performed without using bowel cleansing agent to avoid the risk of intestinal perforation. In CS, same way as US, the entire colon was observed and categorized into 7 segments. The severity was scored using the UCEIS, since it has been reported that the UCEIS may correlate with the severity of IMC (Supplementary Table 1) [27 (link)-29 (link)]. All endoscopic findings were evaluated by 3 experienced gastroenterologists (T.K., S.O., and K.S.), each with more than 6 years of CS experience. They were aware of the IMC diagnosis but were blinded to the patient’s clinical information and US findings.