1. Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Internal Medicine and Institute of Gastroenterology, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Division of Gastroenterology, Department of Internal Medicine, National Health Insurance Service Ilsan Hospital, Goyang, Korea.
4. Department of Gastroenterology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.
5. Division of Gastroenterology, Department of Internal Medicine, Chonnam National University Hospital, Gwangju, Korea.