1. Department of Gastroenterology and Hepatology, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan
2. Department of Endoscopic Diagnostics and Therapeutics, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan
3. Department of Neurosurgery, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan