1. Department of Internal Medicine, Kangbuk Samsung Hospital; Sungkyunkwan University School of Medicine; Seoul Korea
2. Division of Gastroenterology, Department of Medicine, Samsung Medical Center; Sungkyunkwan University School of Medicine; Seoul Korea
3. Digestive Endoscopic Center; Seoul Song Do Colorectal Hospital; Seoul Korea
4. Department of Internal Medicine and Institute of Gastroenterology; Yonsei University College of Medicine; Seoul Korea
5. Department of Internal Medicine, College of Medicine; Dongguk University Ilsan Hospital; Goyang Korea
6. Department of Internal Medicine; Seoul National University Boramae Hospital; Seoul Korea