Received: 30 August 2019
Accepted: 9 October 2019
First Online: 2 November 2019
Ethics approval and consent to participate
: The study was approved by the institutional review board of the Hakodate Central Hospital, Hakodate, Japan (approval number: 2016-2). Written informed consent was obtained from all the patients.
: All authors read and approved the final manuscript.
: The authors declare that they have no competing interests.