1. Department of Gastroenterology, Aizu Medical Center, Fukushima Medical University, 21-2 Kawahigashi Aizuwakamatsu, Fukushima 969-3482, Japan
2. Department of Internal Medicine, Minamiaizu Prefectural Hospital, 14-1 Nagata Minamiaizu, Fukushima 967-0006, Japan
3. Department of Gastroenterology, Dokkyo Medical University School of Medicine, 880 Kitakobayashi Mibu, Tochigi 321-0293, Japan