Practical Step 5: Preoperative Ultrasound Assessment for Arteriovenous Fistula
The “lifeline” of dialysis patients is the key to long-term hemodialysis treatment. A mature, unobstructed, and durable fistula means stability and safety for patients in their dialysis life. However, the success of a fistula depends not only on the surgical skills of the operator, but more on accurate preoperative assessment and scientific planning.
Clinical studies have shown that systematic preoperative vascular ultrasound assessment can significantly improve the primary success rate and long-term patency rate of fistulas.
To sum it up in one sentence: See clearly before surgery, and go far after surgery.
Pre-Assessment Preparation: Standardized Procedures Ensure Assessment Quality
1. Equipment Requirements
– High-frequency linear array probe (≥7.5 MHz)
– Equipped with color Doppler and spectral Doppler functions
– Provided with accurate measurement tools
2. Patient Preparation
– Keep the extremities warm before the examination (room temperature ＞24℃)
– Assume a supine position with upper extremities abducted and externally rotated
– Fully expose the examination area
3. Systematic Scanning Sequence
– Systematically scan from the wrist to the elbow
– Conduct a comparative assessment of both upper extremities
– Mark suspicious areas as key points
Assessment of the Arterial System
Vessel Diameter Requirement: The internal diameter of the radial artery/ulnar artery should be ≥ 1.5–2.0 mm.
Intimal Condition: Intima-media thickness (< 0.5 mm), presence of calcification, plaques, or stenosis.
Hemodynamics: Peak systolic velocity (normal > 50 cm/s), resistance index (RI < 0.8 is ideal). Compression
Response: Whether blood flow decreases significantly after light probe compression, used to judge compliance. Clinical Decision Points:
> Radial artery diameter < 1.5 mm → Significantly increased risk of surgical failure
> Radial artery diameter 1.5–2.0 mm → Comprehensive assessment required
> Radial artery diameter > 2.0 mm → Ideal candidate for surgery
Assessment of the Venous System
Venous Caliber: The internal diameter of the cephalic vein/basilic vein should be ≥ 2.0–2.5 mm (measured under tourniquet compression, with a diameter increase of ＞ 50% after compression).
Diameter Continuity: Check for the presence of branches, stenosis, or thrombosis (the lumen completely disappears upon full compression). Avoid selecting severely tortuous veins.
Depth Assessment: A distance of ＜ 6 mm from the skin surface is optimal for easy puncture.
Valve Location: Multiple valves or valvular dysfunction may affect the anastomosis effect.
Practical Tips:
> Use a tourniquet to fully dilate the vein.
> If necessary, perform a fist-clenching maneuver to observe venous distensibility.
> Mark the venous course to facilitate surgical localization.
Arteriovenous Matching
In principle, the establishment of vascular access should follow the order of upper extremities first, then lower extremities; distal sites first, then proximal sites; non-dominant side first, then dominant side.The priority sequence for upper extremity autologous arteriovenous fistulas (AVF) is as follows:
> Wrist autologous arteriovenous fistula (radial artery-cephalic vein is the most common; ulnar artery-basilic vein)
> Forearm transposition autologous arteriovenous fistula (mainly radial artery-basilic vein transposition)
> Elbow autologous arteriovenous fistula (brachial artery-cephalic vein; brachial artery-median cubital vein; brachial artery-basilic vein)
> Lower extremity autologous arteriovenous fistula (great saphenous vein-femoral artery; great saphenous vein-anterior/posterior tibial artery; great saphenous vein-dorsalis pedis artery)
Common anastomosis methods for autologous arteriovenous fistulas include end-to-end anastomosis, end-to-side anastomosis, and side-to-side anastomosis, among which end-to-side anastomosis is the most prevalent.
Comprehensively evaluate arterial flow and venous capacity to select the most appropriate anastomosis combination.
Meanwhile, assess the direction of collateral blood flow to prevent postoperative steal syndrome.
Assessment Sequence
Ultrasound Assessment Sequence for Autologous AVF: Along the blood flow direction of the fistula, sequentially evaluate the inflow artery, anastomosis, fistula vein, and the entire vascular segment from the cephalic vein arch joining the subclavian vein or the basilic vein joining the axillary vein.
Ultrasound Assessment Sequence for AVG: Along the blood flow direction of the fistula, sequentially evaluate the inflow artery, arterial anastomosis, the entire segment of the graft, venous anastomosis, autologous outflow vein, and the entire vascular segment from the cephalic vein arch joining the subclavian vein or the basilic vein joining the axillary vein.
The content of ultrasound assessment for arteriovenous dialysis access includes blood flow volume, resistance index (RI), vascular morphology and structure (including vessel diameter, intima-media thickness, calcification status, vascular course and depth), stenosis site (including vessel diameter, length, and peak systolic velocity ratio (PSVR)), and thrombosis status (including site, nature, and thrombus volume, etc.).
Preoperative ultrasound assessment for arteriovenous fistula is not just a step in the process, but the cornerstone for laying the quality of the dialysis lifeline. From vessel selection and anastomosis design to long-term management, ultrasound makes everything “traceable”. As surgeons often say, “Ten minutes of ultrasound before surgery is better than ten repairs after surgery.”
SonoMaxx handheld ultrasound is emerging as a new powerful tool for vascular access management — enabling full-process visual management from preoperative assessment and postoperative follow-up to complication monitoring. Let us start with that probe before surgery and use ultrasound to build a “perfect” lifeline for patients.
☛ Next Episode Preview | Arteriovenous Fistula Maturation Assessment: Has Your Fistula “Grown Up”?
After the successful establishment of an arteriovenous fistula, how to judge its maturation? The next episode will provide you with a detailed interpretation of the maturation criteria and intervention timing.