1. Department of Surgery, School of Medicine, Toho University, Tokyo 143‑8541, Japan
2. Department of Gastroenterological Surgery and Clinical Oncology, Graduate School of Medicine, Toho University, Tokyo 143‑8541, Japan
3. Port Square Kashiwado Clinic, Kashiwado Memorial Foundation, Chiba 260‑0025, Japan
4. Department of Neurological Surgery, Graduate School of Medicine, Chiba University, Chiba 260‑8670, Japan