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