1. Digestive Disease Center and Research Institute, Department of Internal Medicine; Soonchunhyang University School of Medicine; Bucheon Korea
2. Division of Gastroenterology, Department of Medicine; Chulalongkorn University; Bangkok Thailand
3. Department of Gastroenterology, Graduate School of Medicine; The University of Tokyo; 7-3-1 Hongo Bunkyo-ku Tokyo 113-8655 Japan