1. Department of Gastrointestinal Surgery, Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, 266003, China
2. Department of Gastrointestinal Surgery, the People’s Hospital of Jimo District of Qingdao, Shandong Province, 266200, China
3. Department of General Surgery, the Second Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, 266042, China