1. Department of Surgery, Uijeongbu St. Mary's Hospital, The Catholic University of Korea, Uijeongbu-si, Korea.
2. Epidemiology Study Cluster of Uijeongbu St. Mary's Hospital, Uijeongbu St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Uijeongbu-si, Korea.
3. Department of Biostatistics, College of Medicine, The Catholic University of Korea, Uijeongbu-si, Korea.