Duplex of Renal Arteries: Location Points and Stenosis Criteria (RAR, PSV, tardus-parvus, RI)

Location Points and Technique

PSV is recorded along the entire length of the renal artery—from the aortic ostium to the renal hilum (AbuRahma et al., 2012). Aortic PSV is measured at the level of visceral (mesenteric) arteries for RAR calculation (Blagodir, 2026). Intrarenal blood flow (RI, AT, waveform) is assessed in interlobar arteries adjacent to the pyramids (Diagnostic Ultrasound Vascular, 2025).

Direct and Indirect Criteria

ESVS 2025 divides parameters into direct (PSV in the stenosis zone and RAR—the ratio of renal artery PSV to unchanged aortic PSV) and indirect (RI in the interlobar artery, waveform shape, flow acceleration, and prolonged acceleration time—tardus-parvus, measured distal to the stenosis). Combining direct and indirect parameters increases diagnostic accuracy.

CriterionValueInterpretationPSV in renal artery>180–200 cm/s (ESC 2024: >200–250 cm/s)Stenosis >50–60 %RAR (renal PSV / aortic PSV)≥3.5Stenosis ≥60 %Acceleration time (AT) intrarenal>70–100 msIndirect sign of significant proximal stenosisIntrarenal spectrumtardus-parvusIndirect sign of proximal stenosisOcclusionNo flow (CDI/energy/spectrum), kidney <8 cmComplete obstruction

Source: Table 2.1 (Blagodir, 2026), considering ACC and ESC 2024.

Classification by RAR, PSV, and Kidney Length

According to Diagnostic Medical Sonography (2023, Table 25-1): normal—RAR <3.5, PSV <180 cm/s, no post-stenotic turbulence, kidney length 9–13 cm; <60 %—RAR <3.5, PSV ≥180 cm/s; ≥60 %—RAR ≥3.5, PSV ≥180 cm/s, post-stenotic turbulence present; occlusion—PSV/RAR not determined, kidney length <8 cm.

RI and Side Difference

RI = (PSV − EDV)/PSV; measured in the interlobar artery (ESVS 2025). RI value >0.7 in adults usually indicates pathological flow resistance (Diagnostic Ultrasound Vascular, 2025). RI difference >0.05 between sides is a sign of ipsilateral stenosis (review article, 2008; Schwerk et al., 1994: sensitivity 82%/specificity 92% for >50%; 100%/94% for >60%).

Additional Indices and Confirmation

Acceleration index (AI) and maximum systolic acceleration (ACCmax) as screening tests for RAS outperform PI/RI (Burdick et al., J Hypertens 1996). AT and AI are less specific than the main renal artery PSV and should not be used in isolation (Diagnostic Ultrasound Vascular, 2025). Inconclusive duplex indicates MRA/CTA (class I, ESC 2024 / ACR); catheter angiography is the reference but invasive method.

Documented Parameters

Minimum set (Blagodir, 2026): PSV and aortic diameter at the level of visceral arteries; segmental PSV, plaque, turbulence, and RAR for each renal artery; presence and side of accessory arteries; intrarenal blood flow (AT, tardus-parvus, RI, RI side difference); length of both kidneys and side difference; if stent present—localization and signs of restenosis.