1 Department of Gastrointestinal Surgery, The Affiliated Hospital of Qingdao University, No. 16 Jiangsu Road, Qingdao, 266000, Shandong, China.
2 Department of Gastrointestinal Surgery, The Affiliated Hospital of Qingdao University, No. 16 Jiangsu Road, Qingdao, 266000, Shandong, China. liyu11920@hotmail.com.