1. Digestive Disease Center and Research Institute, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Soonchunhyang University School of Medicine, Bucheon, Korea
2. Digestive Disease Center and Research Institute, Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Soonchunhyang University School of Medicine, Cheonan, Korea
3. Digestive Disease Center and Research Institute, Department of Internal Medicine, Soonchunhyang University Seoul Hospital, Soonchunhyang University School of Medicine, Seoul, Korea