Many guidelines at home and abroad advocate that arteriovenous fistula should be the first choice of permanent vascular access, but it is easy to form thrombus in a short time after arteriovenous fistula molding, resulting in internal fistula stenosis or occlusion. In this study, the investigators plan to screen the patients with arteriovenous fistula in the blood purification center of our hospital. Through the study design of random grouping and open label, the investigators will discuss the use of low molecular weight heparin or warfarin to prevent thrombosis in a short period of time after arteriovenous fistula operation. According to the research results, the investigators will understand efficacy and safety of short-term postoperative anticoagulant therapy to prevente thrombosis in arterovenous fistula.

Inclusion Criteria:

• After AVF formation or balloon dilation surgery, there were no significant signs of oozing or bleeding at the surgical incision and operative site observed within 12-24 hours.
• The patient is willing to accept short-term anticoagulant therapy after the surgery, bear related risks, and sign an informed consent form.
• The patient is willing to cooperate with this study, undergo data collection related to the research, and relevant clinical examinations.

Exclusion Criteria.

• Age >80 years;
• Concurrent hematologic diseases that can affect coagulation function;
• Concurrent comorbidities that can affect the patient's bleeding or coagulation functions, such as liver cirrhosis;
• Concurrent active bleeding disorders, such as active gastrointestinal ulcers or active lupus;
• History of major organ bleeding (e.g., intracranial or gastrointestinal) or surgery within the past six months;
• Unwillingness to participate in this study.