1. Division of Gastroenterology and Hepatology, Graduate School of Medical and Dental Science, Niigata University, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8520, Japan
2. Department of Internal Medicine, Kameda Daiichi Hospital, 2-5-22 Nishimachi, Konan-ku, Niigata 950-0165, Japan
3. Department of Gastroenterology and Hepatology, Nagaoka Red Cross Hospital, 2-297-1 Senshu, Nagaoka 940-2085, Japan
4. Department of Gastroenterology and Hepatology, Uonuma Institute of Community Medicine, Niigata University Medical and Dental Hospital, 4132 Urasa, Minamiuonuma 949-7302, Japan