1. Department of Surgery, School of Medicine, Toho University, Tokyo 143‑8541, Japan
2. Department of Gastroenterology, Graduate School of Medicine, Chiba University, Chiba‑shi, Chiba 260‑8677, Japan
3. Department of Surgery, Chiba Cancer Center, Chiba‑shi, Chiba 260‑8717, Japan
4. Department of Gastroenterology, Japan Community Health Care Organization Chiba Hospital, Chiba‑shi, Chiba 260‑8710, Japan
5. Department of Gastroenterology, Funabashi Municipal Medical Center, Funabashi, Chiba 273‑8588, Japan
6. Department of Gastroenterology, Kimitsu Chuo Hospital, Kimitsu, Chiba 292‑8535, Japan
7. Department of Gastroenterology, Japan Community Health Care Organization Funabashi Central Hospital, Funabashi, Chiba 273‑8556, Japan