Practical Step 3: Ultrasound Assessment of Arteriovenous Fistula Stenosis
Arteriovenous fistula stenosis is the number one culprit leading to hemodialysis access dysfunction.
Causes of Arteriovenous Fistula Stenosis
Common predisposing factors include vascular wall injury caused by repeated punctures, high-flow state at the arteriovenous anastomosis, local blood flow disturbance, or thrombosis
Early identification of stenosis can prolong the service life of the fistula, reduce the rate of emergency access catheterization, and decrease the risk of infection and dialysis interruption.
Ultrasound Examination Steps and Parameters
It is recommended to perform continuous scanning along the path from the arterial end → anastomosis → main fistula tract → puncture segment → venous return end, while keeping the probe aligned with the direction of blood flow
A high-frequency linear array probe (7–15 MHz) is preferred. The SonoMaxx handheld ultrasound, with its portability, compact size, ease of operation, and real-time imaging capability, is extremely convenient for bedside use. It enables dynamic monitoring at any time and is thus ideally suited for bedside assessment of arteriovenous fistulas.
The following indicators suggest vascular stenosis:
- Blood flow: Under stable systemic hemodynamic conditions, the native AVF (arteriovenous fistula) natural blood flow is < 500 mL/min, and the AVG (arteriovenous graft) natural blood flow is < 600 mL/min.
- Vascular inner diameter: The local venous inner diameter ≤ 1.7 mm or the long-segment venous inner diameter ≤ 2.0 mm with a length ≥ 20 mm; the arterial inner diameter ≤ 2.0 mm. For patients with a local venous inner diameter between 1.8 and 2.0 mm or an arterial inner diameter between 2.0 and 2.5 mm, a comprehensive judgment should be made based on the patient’s clinical symptoms, abnormal signs, and the feasibility of effective HD (hemodialysis).
- RI (Resistive Index): RI > 0.5.
- PSVR (Peak Systolic Velocity Ratio): PSVR > 4.
Common Stenotic Sites and Their Ultrasound Manifestations
01
Stenosis at the Anastomosis
The most common site.
Ultrasound manifestations: Sudden caliber change, jet-like enhancement of blood flow, and significant elevation of PSV.
02
Stenosis at the Puncture Segment
Associated with repeated punctures and scar formation.
Manifestations: Thickened vessel wall, irregular lumen, and localized elevation of blood flow velocity.
03
Stenosis of the Centripetal Vein
May lead to distal dilation of the fistula and decreased blood flow.
Manifestations: Decreased blood flow velocity in deep blood vessels, restricted venous return, and distal dilation. A low-frequency probe is often required for the examination of deep blood vessels.
Ultrasound assessment before and after artificial arteriovenous fistula surgery is simple, convenient, and cost-effective, with excellent clinical application value and great convenience for patients. Handheld ultrasound makes the protection of dialysis access more efficient and proactive.
☛ Next Episode Preview | A Comprehensive Interpretation of the Three Major Hemodialysis Accesses
In the next episode, we will temporarily move away from images and return to the fundamentals, taking you to a comprehensive understanding of the “life bridges” for hemodialysis patients—autologous arteriovenous fistula (AVF), arteriovenous graft (AVG), and central venous catheter (CVC).