Duplex Ultrasound of Upper Extremity Arteries: Protocol and Stenosis Criteria
The Role of AIUM 2025 in the Study Protocol
The updated Practice Parameter for Peripheral Arterial Ultrasound AIUM 2025 sets the framework for peripheral arterial examination: B-mode, color or power Doppler, spectral Doppler, and clinically oriented conclusion. For the upper extremities, the document does not replace local laboratory validation but establishes principles: accessible segments along the artery are examined, the pathological area is compared with a normal proximal segment, and the degree of stenosis is formulated based on the combination of image, color, and spectrum.
Practically, this means the protocol should not be limited to the phrase "flow preserved." Localization, the nature of the wall and lumen, spectrum shape, PSV, and, in case of stenosis, the velocity ratio are needed.
Indications for Duplex of Upper Extremity Arteries
The study is performed when occlusive-stenotic lesions, embolism or thrombosis, hand ischemia, subclavian steal syndrome, arterial trauma, aneurysm, pseudoaneurysm, arteriovenous communication, vascular access complications, post-reconstruction or endovascular treatment follow-up are suspected. A separate task is the preoperative assessment of the radial and ulnar arteries when planning access or reconstruction.
The clinical request should be reflected in the scanning volume. For pain and coldness of the hand, distal arteries and arches are important; for pressure differences between arms, the subclavian-axillary segment and the direction of blood flow in the vertebral artery serve as auxiliary signs of proximal lesions.
Segments to Describe
The standard scanning route is from proximal inflow to periphery. The examination usually starts with the subclavian artery, continues through the axillary and brachial, then evaluates the bifurcation of the brachial artery, radial and ulnar arteries. Palmar arches and digital arteries are included for distal ischemia, trauma, vasospastic or embolic changes.
| Segment | What to Document in the Protocol |
|---|---|
| Subclavian artery | Patency, plaque/thrombus, local acceleration, post-stenotic spectrum; if inflow lesion is suspected, connection with vertebral blood flow. |
| Axillary artery | External compression, post-traumatic changes, aneurysmal dilation, spectrum before and after the area of interest. |
| Brachial artery | Lumen, wall, spectrum, PSV; for vascular access, puncture sites and possible pseudoaneurysms. |
| Radial and ulnar arteries | Patency, flow symmetry, distal spectrum, signs of spasm, thrombosis, or embolism. |
| Palmar arches and digital arteries | Assessed as indicated: presence of flow, direction, spectrum damping, distal perfusion. |
Scanning Technique and Settings
A linear transducer with the highest possible frequency providing sufficient penetration is used. B-mode is needed for the wall, calcifications, thrombus, plaque, aneurysm, or pseudoaneurysm. Color Doppler is adjusted to not miss low-velocity flow: gain, velocity scale, and wall filter are corrected. Spectral Doppler is obtained with angle correction; for PSV measurements, the Doppler angle should be reproducible and not exceed 60°.
In focal lesions, at least three spectra are documented: proximal to the stenosis in a relatively normal segment, directly at the maximum acceleration zone, and distal. This scheme allows calculating the PSV ratio and distinguishing local stenosis from overall inflow reduction.
Normal Spectrum of Upper Extremity Arteries
At rest, large peripheral limb arteries typically show a multiphasic high-resistance spectrum: rapid systolic rise, early diastolic reverse component, and subsequent small antegrade component. After warming, physical exertion, vasodilation, or distal hyperemia, the spectrum may become lower resistance. Therefore, the waveform is always interpreted with clinical context, limb temperature, symmetry, and findings in adjacent segments.
Pathological signs include local color aliasing, lumen filling with thrombus, loss of pulsatility, spectral broadening, monophasic damped distal flow, and collateral flow restoration.
Stenosis Criteria by AIUM 2025
AIUM 2025 uses not absolute PSV for all arteries but a velocity ratio: PSV at the maximum stenosis zone divided by PSV in the nearest normal proximal segment. This is especially important for the upper extremities, where absolute velocities depend on the measurement level, temperature, peripheral resistance, vascular access, and proximal inflow.
| Finding | Quantitative Criterion | Formulation |
|---|---|---|
| Focal acceleration with color aliasing and spectral broadening | PSV ratio ≥2:1 | Diameter stenosis ≥50%. |
| Sharp local acceleration, marked turbulence, distal damping | PSV ratio ≥4:1 | Diameter stenosis ≥75%. |
| No reliable flow in the lumen with optimal settings | Velocity not measurable | Occlusion of the examined segment. |
| Distal monophasic tardus-like spectrum without visualization of the maximum narrowing zone | PSV ratio not calculated | Indirect sign of proximal hemodynamically significant lesion; requires search for stenosis level. |
If the proximal "normal" segment is itself affected or the flow is globally low, the PSV ratio may be unreliable. In such a situation, the conclusion indicates the method's limitation and describes the combination of signs: lumen morphology, color pattern, collaterals, and distal spectrum.
Subclavian Segment and Proximal Inflow
Subclavian artery lesions often manifest not only as local acceleration but also as changes in spectra further down the limb. Distal to the stenosis, monophasic, smoothed, low-pulsation flow may occur. If subclavian steal is suspected, documenting the direction and shape of blood flow in the vertebral artery is useful, as a change in flow direction supports the diagnosis of proximal hemodynamic obstruction.
In the protocol, it is important to specify the side, exact segment, accessibility of the origin, presence of calcification or acoustic shadowing, and the ability to reliably measure PSV. If the origin of the subclavian artery is not visualized, the conclusion is based on available direct and indirect signs.
How to Write the Conclusion
Optimal conclusion structure: 1) examined segments; 2) patency; 3) lesion localization; 4) morphology of plaque, thrombus, aneurysm, or pseudoaneurysm; 5) spectral characteristics; 6) PSV and velocity ratio in stenosis; 7) degree of stenosis or occlusion; 8) distal hemodynamic consequences.
Example formulation: "In the mid-third of the left brachial artery, a focal lumen narrowing with color aliasing is visualized. PSV in stenosis — specify measured value, PSV in proximal unchanged segment — specify value, PSV ratio ≥2:1. Ultrasound signs of stenosis ≥50%, distal flow preserved, spectrum monophasic/multiphasic." Numbers are entered from actual measurements, not from a template.
Common Mistakes
- Assessing stenosis only by color without spectral PSV and velocity ratio.
- Measuring PSV at an angle greater than 60° or without correct angle alignment along the flow.
- Comparing the stenosis zone with the distal rather than proximal normal segment.
- Ignoring proximal inflow lesion with monophasic spectra in all arm arteries.
- Formulating "stenosis present" without percentage by criteria ≥50% or ≥75% when the PSV ratio allows it.
Frequently asked questions
Are absolute PSV norms needed for the radial and ulnar arteries?
In the AIUM 2025 parameter, the focus is not on universal absolute PSV for each segment but on the local PSV ratio in stenosis to PSV in the nearest normal proximal segment. For clinically significant stenosis, thresholds of ≥2:1 and ≥4:1 are used.
How to state the degree of stenosis if the maximum acceleration zone is not visible?
Indirect signs should be described: distal monophasic damped spectrum, reduced pulsatility, collaterals, absence of normal proximal signal. The percentage of stenosis by PSV ratio is not indicated if the velocity ratio cannot be calculated.
What is considered occlusion in duplex of upper extremity arteries?
Occlusion is the absence of detectable blood flow in the lumen of the examined segment with adequate color/power and spectral Doppler settings, usually with possible collateral or reconstituted flow distal to it.