1. Department of Urology Sapporo Medical University School of Medicine Sapporo Japan
2. Department of Urology Hakodate Koseiin Hakodate Goryoukaku Hospital Hakodate Japan
3. Department of Urology Japanese Red Cross Asahikawa Hospital Asahikawa Japan
4. Department of Urology Sunagawa City Medical Center Sunagawa Japan
5. Department of Urology Oji General Hospital Tomakomai Japan
6. Department of Urology Steel Memorial Muroran Hospital Muroran Japan
7. Department of Urology NTT East Corporation Sapporo Hospital Sapporo Japan
8. Department of Urology Takikawa Municipal Hospital Takikawa Japan
9. Department of Urology Muroran City General Hospital Muroran Japan
10. Department of Urology Japanese Red Cross Kushiro Hospital Kushiro Japan
11. Department of Biostatistics Sapporo Medical University School of Medicine Sapporo Japan