1. Second Department of Internal Medicine, Osaka Medical College, Takatsuki, Osaka, Japan
2. Department of Gastroenterology, First Towakai Hospital, Takatsuki, Japan
3. Endoscopic Center, Osaka Medical College Hospital, 2-7, Daigakumachi Takatsuki, Osaka, 569-8686, Japan
4. Department of Gastroenterology, Shiroyama Hospital, Habikino, Japan
5. Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan
6. Department of Medical Statistics, Osaka City University Graduate School of Medicine, Osaka, Japan