1. Department of Neurosurgery, Central South University, Xiangya School of Medicine Affiliated Haikou Hospital, Haikou, China.
2. Department of Gastroenterology, Hainan General Hospital, Hainan Affiliated Hospital of Hainan Medical University, Haikou, China.
3. Department of Surgery, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
4. National Center for Global Health and Medicine, Tokyo, Japan.