1. Division of Gastroenterology and Hepatology, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
2. Department of Gastroenterology, Nagaoka Red Cross Hospital, Niigata, Japan.
3. Department of Gastroenterology, Saiseikai Kawaguchi General Hospital, Saitama, Japan.
4. Division of Gastroenterology and Hepatology, Saiseikai Niigata Daini Hospital, Niigata, Japan.
5. Department of Gastroenterology, Niigata Cancer Center Hospital, Niigata, Japan.