Common causes of preoperative coagulation disorders and choice of optimal operation time        LOU Wen-hui. Department of Surgery, Zhongshan Hospital, Fudan University， Shanghai 200032，China
Abstract    Coagulation disorders are main threats to safe operation. Thorough preoperative coagulation evaluation is crucial. Generally, coagulation disorders fall into two categories: congential and acquired coagulopathy. Hemopilia A and B belong to the former category. The acquired coagulopathy includes vitamin K deficiency, intake of anticoagulant drugs, hepatic failure, renal failure, thrombocytopenia and thrombocytopathy, hypothermia etc. For selective operation, it is better to perform after coagulation disorders are rectified to ensure the patient safey. In emergency cases, active treatment should be taken to restore coagulation as possible as it can.