Received: 1 October 2017
Accepted: 21 May 2018
First Online: 31 May 2018
: TK and SS are urologists.
: The present study was approved by the Institutional Review Board (IRB) of Saku Central Hospital (Reference number: R201510–04). Consent was obtained from all participants included in the study through the opt-out method in accordance with the national regulations and the ethical guidelines for clinical studies in Japan. The IRB waived the requirement for written informed consent due to the retrospective nature of the present analysis.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.