Received: 3 March 2019
Accepted: 23 July 2019
First Online: 9 August 2019
Ethics approval and consent to participate
: The study was conducted according to the Helsinki Declaration. The main institution, the Department of Gastroenterological Surgery, Graduate School of Medicine, Yokohama City University (IRB approval number: B120705037), and all other participating institutions approved the study protocol.
: Not applicable.
: The authors declare that they have no competing interests.