Received: 28 May 2019
Accepted: 30 September 2019
First Online: 27 October 2019
Ethics approval and consent to participate
: This study was approved by the institutional review board of Hokkaido University (No.012–0360). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from all individual participants included in the study.
: Not applicable.
: EK has the following financial relationships to disclose: grant/research funding from Muto Co Ltd. Japan, Smith & Nephew Endoscopy Japan, Olympus Terumo Biomaterials Japan, and Yufu Itonaga Co Ltd. Japan. All other authors declare that they have no conflict of interest.