1. Department of Gastroenterology, Faculty of Medicine, Oita University, 1-1, Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
2. Department of Gastroenterology, Oita San-ai Medical Center, 1213 Ichi, Oita 870-1151, Japan
3. Department of Gastroenterology, Oita Koseiren Tsurumi Hospital, 4333, Tsurumi, Beppu, Oita 874-8585, Japan
4. Department of Advanced Medical Sciences, Faculty of Medicine, Oita University, 1-1, Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan