1. Division of Gastroenterology, Department of Internal Medicine, Inje University Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea
2. Department of Internal Medicine, The Graduate School, Yonsei University College of Medicine, Seoul, Korea
3. Division of Gastroenterology, Department of Internal Medicine, Gachon University Gil Medical Center, Incheon, Korea
4. Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea