This study is aimed to assess the value of three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) in hemodialysis patients with occlusive disease in arteriovenous fistula (AVF). All participants will receive 3D-TOF-MRA and ultrasound to detect the stenosis degree of AVF.

The Principle of 3D-TOF-MRA is based on the "flow effect" of MR. In the GE sequence of MRA imaging, the effect of RF pulses makes the protons in the stationary tissue in the active layer in a saturated state, and the longitudinal magnetization disappears. When the inflow blood appears, its protons are in an unsaturated state and have a high degree of longitudinal magnetization. In this way, a clear difference is formed between saturated tissue and unsaturated flowing blood to display blood vessels. Therefore as a non-invasive and safe method for diagnosing vascular diseases, 3D-TOF-MRA is used widely in cerebrovascular diseases. However, there are currently no studies using 3D-TOF-MRA to diagnose arteriovenous fistula (AVF) stenosis in hemodialysis patients. This project plans to use 3D-TOF-MRA to detect AVF stenosis in hemodialysis patients to provide a safe and effective diagnostic method for patients with end-stage renal failure.

Inclusion Criteria:

• hemodialysis patients suspected of occlusive disease in arteriovenous fistula (AVF);
• persistent edema of the limb with the fistula;
• decreased pulse or fremitus in anastomotic astium
• increase in venous pressure; blood flow at the access of less than 200 mL/min;

Exclusion Criteria:

• previous endovascular recanalization with stent or graft placement;
• contraindications to magnetic resonance imaging (MRI) examination;
• platelet(PLT)<60*10^9/L or international normalized ratio (INR)>1.5; 4. important organ function failure or other serious illness; 5. Allergic to antiplatelet drug, anticoagulant drug, anaesthetic drug and contrast material.

Individual participant data will not be made avaliable.