1. Department of Gastroenterology, School of Medicine, Fukushima Medical University, Fukushima, Japan
2. Department of Gastroenterology, Saiseikai Fukushima General Hospital, Fukushima, Japan
3. Department of Gastroenterology, Fukushima Red Cross Hospital, Fukushima, Japan
4. Department of Endoscopy, Fukushima Medical University Hospital, Fukushima, Japan
5. Department of Hepato-Biliary-Pancreatic and Transplant Surgery, School of Medicine, Fukushima Medical University, Fukushima, Japan