1. Department of Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
4. Department of Surgery, SMG-SNU Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea.