1. Department of General Surgery, The Second Affiliated Hospital of Qiqihar Medical University, Qiqihar, Heilongjiang 161006, P.R. China
2. Department of Rotation, The Second Affiliated Hospital of Qiqihar Medical University, Qiqihar, Heilongjiang 161006, P.R. China
3. Department of General Surgery, First Affiliated Hospital of Jiamusi University, Jiamusi, Heilongjiang 154000, P.R. China