1. Department of Hepatobiliary and Pancreatic Surgery; Graduate School of Medicine; Tokyo Medical and Dental University; 1-5-45 Yushima Bunkyo-ku Tokyo 113-8519 Japan
2. Department of Surgery; Toho University Faculty of Medicine; Tokyo Japan
3. Department of Surgery; Iwate Medical University School of Medicine; Iwate Japan
4. Department of Surgery; School of Medicine; Keio University; Tokyo Japan