Renal arteries (native Doppler) — Reference values
Renal arteries (native Doppler) — Reference values: Common clinical indications, Minimum technical protocol, Main renal artery peak systolic velocity.
Renal artery stenosis thresholds vary across laboratories and guidelines. For international safety: clearly normal values are green; peak velocities from 180 to 199 cm/s, renal-to-aortic ratio close to 3.5, or isolated indirect findings are yellow; combined high velocity, renal-to-aortic ratio of 3.5 or higher, post-stenotic turbulence, or tardus-parvus waveform are red. Doppler findings should be interpreted with clinical context, renal function, kidney asymmetry, and acoustic window quality.
Measurements and reference values
| Measurement | Usual value | Note |
|---|---|---|
| Common clinical indications | Resistant or abrupt-onset hypertension; progressive or unexpected renal function decline; renal function decline after angiotensin-converting enzyme inhibitor or angiotensin receptor blocker therapy; abdominal bruit; kidney size difference greater than 2 cm; follow-up of known stenosis, angioplasty, or stent; suspected renal infarction, aortic dissection, aneurysm, pseudoaneurysm, arteriovenous fistula, or renal venous disease. | When renovascular hypertension is suspected, duplex Doppler is a widely accepted initial option when the acoustic window is adequate.Source: ACR-AIUM-SPR-SRU Practice Parameter for Duplex Sonography of Native Renal Vessels, 2023; ACR Appropriateness Criteria Renovascular Hypertension |
| Minimum technical protocol | Measure the longest length of each kidney; assess the aorta at the renal artery level; map the main renal arteries from origin to hilum, including proximal, mid, and distal segments; look for accessory arteries when possible; record intrarenal waveforms in upper, mid, and lower poles; apply Doppler angle correction and keep the angle at 60 degrees or less. | If a segment is not visualized, the report should state that clearly rather than assuming normality.Source: ACR-AIUM-SPR-SRU Practice Parameter for Duplex Sonography of Native Renal Vessels, 2023 |
| Main renal artery peak systolic velocity | < 180 cm/s | Usually normal when isolated and waveform shape is preserved. Values from 180 to 199 cm/s are borderline in many protocols; 200 cm/s or higher increases suspicion for hemodynamically relevant stenosis, especially with an elevated renal-to-aortic ratio.Source: ACR-AIUM-SPR-SRU Practice Parameter; Schaberle et al. Ultrasound diagnostics of renal artery stenosis; Ultrasoundpaedia renal artery protocol |
| Renal-to-aortic ratio | < 3.5 | Calculated as the highest renal artery peak systolic velocity divided by the aortic peak systolic velocity at the renal artery level. A ratio of 3.5 or higher is a strong criterion for significant stenosis when the aortic velocity is reliable.Source: ACR-AIUM-SPR-SRU Practice Parameter; Schaberle et al. Ultrasound diagnostics of renal artery stenosis; Ultrasoundpaedia renal artery protocol |
| Intrarenal acceleration time | <= 70 ms | Time greater than 70 ms, especially with a tardus-parvus waveform, suggests proximal stenosis. In isolation it may be borderline and should be compared with direct criteria.Source: ACR-AIUM-SPR-SRU Practice Parameter; Ultrasoundpaedia renal artery protocol |
| Intrarenal acceleration index | >= 300 cm/s² | Values below 300 cm/s² support a tardus-parvus pattern, but they are most useful when combined with prolonged acceleration time and direct criteria.Source: ACR-AIUM-SPR-SRU Practice Parameter; Ultrasoundpaedia renal artery protocol |
| Intrarenal resistive index | Usually < 0.70 | Values from 0.70 to 0.79 suggest increased parenchymal resistance or relevant clinical context. A value of 0.80 or higher is abnormal and often reflects chronic parenchymal disease or worse prognosis, but it does not confirm stenosis by itself.Source: ACR-AIUM-SPR-SRU Practice Parameter; Ultrasoundpaedia renal artery protocol |
| Kidney length and asymmetry | Typical adult: 9 to 12 cm; difference > 2 cm is relevant | A small kidney, asymmetry greater than 2 cm, or cortical loss increases suspicion for chronic disease, renal ischemia, or sequelae of longstanding stenosis.Source: ACR-AIUM-SPR-SRU Practice Parameter; StatPearls Renal Artery Stenosis |