1. Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
2. Department of Gastroenterology, JR Tokyo General Hospital, Tokyo, Japan
3. Department of Gastroenterology, Toshiba Hospital, Tokyo, Japan
4. Department of Gastroenterology, Tokyo Metropolitan Police Hospital, Tokyo, Japan
5. Department of Gastroenterology, Kanto Central Hospital, Tokyo, Japan
6. Department of Gastroenterology, Japanese Red Cross Medical Center, Tokyo, Japan