Ito S, Hotta K, Imai K, et al. - Researchers sought to assess the ability of an ultrathin colonoscope (UTC) to assess the whole colon by passing through the stenotic colorectal cancers (CRC) in this prospective observational study. Eligibility was checked for all patients who underwent preoperative colonoscopy for stenotic CRCs at Shizuoka Cancer Center. In total, 100 patients were recruited between September 2017 and February 2019. Ultrathin colonoscopy can be viewed as an alternative to examine the whole colon proximal to the stenosis when standard colonoscopy can not pass through stenotic CRC. Treatment plan can potentially be altered by identifying synchronous neoplasias proximal to the stenosis before surgery.