Received: 27 December 2017
Accepted: 27 March 2018
First Online: 2 May 2018
Ethics approval and consent to participate
: This study was approved by the institutional review boards of Tokyo Medical and Dental University and Matsudo City Hospital (#M2017–237 and #29–14, respectively). This study complies with the principles of the 1964 Declaration of Helsinki in reviewing and publishing information from the patient’s medical records. The requirement for informed consent from each patient was waived because the design of study was retrospective in nature and because of the use of anonymized patient and hospital data.
: The authors declare that they have no competing interests.
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