Received: 8 May 2019
Accepted: 7 June 2019
First Online: 14 June 2019
Ethics approval and consent to participate
: This retrospective cohort study was approved by the ethics committee of Itoigawa General Hospital (#2018-18) and was conducted in accordance with the principles of the Declaration of Helsinki.
: As this study was conducted in a retrospective manner, we did not obtain consent for publication from the participants.
: The authors declare that they have no competing interests.