1. Division of Gastroenterology, Tachikawa General Hospital, Kandamachi 3-2-11, Nagaoka, Niigata 940-8621, Japan
2. Division of Gastroenterology and Hepatology, Graduate School of Medical and Dental Sciences, Niigata University, Asahimachi 1-757, Chuo-ku, Niigata, Niigata 951-8122, Japan