Peak Velocity Criteria for Significant Renal Artery Stenosis
A peak systolic velocity (PSV) of 200 cm/s is the most widely accepted threshold for diagnosing significant renal artery stenosis (≥60%), with a sensitivity of 73-91% and specificity of 75-96%. 1
Primary Diagnostic Criteria for Native Renal Arteries
- PSV cutoff values ranging from 180-300 cm/s have been proposed in various studies, with 200 cm/s being the most commonly used threshold 1
- A renal-to-aortic ratio (RAR) ≥3.5 is a commonly reported secondary criterion that improves specificity when used with PSV measurements 1
- To improve specificity, some authors recommend a higher PSV threshold of 300 cm/s, particularly when the clinical suspicion is high but other findings are equivocal 1
Diagnostic Algorithm for Renal Artery Stenosis
First-Line Assessment:
- Measure PSV in the main renal artery - primary criterion for stenosis detection 1
- Calculate RAR - helps differentiate true stenosis from generally elevated velocities due to hypertension 1
- Assess for side-to-side difference of intrarenal resistance index ≥0.05 - highly specific (97%) for hemodynamically significant stenosis 2, 3
Interpretation of Results:
- PSV ≥200 cm/s suggests stenosis ≥60% (sensitivity 73-91%, specificity 75-96%) 1
- RAR ≥3.5 supports diagnosis of stenosis ≥60% 1
- PSV ≥285 cm/s provides better specificity (90%) but lower sensitivity (67%) 4
Special Considerations for Stented Renal Arteries
- Higher velocity thresholds are required for stented arteries due to altered arterial compliance 1, 5
- For in-stent restenosis, a PSV ≥395 cm/s or RAR ≥5.1 is most predictive of significant stenosis (≥70%) 1, 5
- Chi et al. found that in stented arteries, mean PSV was 382 cm/s and mean RAR was 5.3 in arteries with >60% stenosis 1
Additional Diagnostic Parameters
- A parvus-tardus intrarenal waveform (small peak, slow upstroke) is highly suggestive of proximal stenosis 1
- Acceleration time >70 milliseconds and loss of early systolic peak indicate significant stenosis 1
- Resistive index (RI) >0.80 is not specific for RAS but has been reported as a negative prognostic sign for response to revascularization 1, 6
Potential Pitfalls in Measurement
- Doppler ultrasound is highly operator-dependent and time-consuming 1
- Visualization may be impeded by patient body habitus, bowel gas, dense atherosclerotic plaques, and accessory renal arteries 1
- PSV may be elevated due to hypertension without underlying RAS, making RAR an important complementary measurement 1
- Accessory renal arteries may be missed (detected in only 6 of 34 cases in one study) 4
European Society of Cardiology Guidelines
- The ESC recommends duplex ultrasound as the first-line imaging modality for RAS with a Class I, Level B recommendation 1
- PSV ≥200 cm/s is considered indicative of >50% RAS according to the 2024 ESC guidelines 1
- When DUS is inconclusive, MRA or CTA should be considered (Class I, Level B recommendation) 1