1. Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
2. Department of Surgery, Yonsei University College of Medicine, Seoul, Korea
3. Department of Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea
4. Department of Surgery, Korea University College of Medicine, Seoul, Korea
5. Department of Surgery, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea
6. Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea