Renal Artery Duplex Ultrasound

1. 1

   Patient fasting 6–8 hours to minimise bowel gas. Supine or slight oblique. Curvilinear probe.

2. 2

   Aorta: transverse view at the level of renal arteries (L1–L2). Sample aortic PSV for RAR calculation.

3. 3

   Right renal artery: from aorta, angle probe right. Follow RA origin to hilum. Sample at origin, proximal, and mid-segment.

4. 4

   Left renal artery: rotate/angle left from aorta. Follow posterior and lateral course to left kidney.

5. 5

   Both kidneys: measure length longitudinally. Asymmetry >2cm suggests renovascular disease on smaller side.

6. 6

   Parenchymal Doppler: sample segmental/interlobar arteries in upper, mid, and lower poles. Calculate RI = (PSV−EDV)/PSV.

7. 7

   RAR (renal artery PSV / aortic PSV) >3.5 = significant stenosis. RI >0.80 = poor revascularization prognosis.

• Aorta at renal artery origins — transverse
• Right renal artery — origin + mid segment Doppler
• Left renal artery — origin + mid segment Doppler
• Right renal parenchyma — segmental/interlobar arteries
• Left renal parenchyma — segmental/interlobar arteries
• Kidney lengths — bilateral

• Renal artery PSV at origin
• Renal/aortic ratio (RAR)
• Resistive index (RI) parenchymal
• Kidney size asymmetry
• Post-stenotic turbulence

• Bowel gas is the major limiting factor — patient prep essential
• Accessory renal arteries in 20–30% of patients
• RAR >3.5 indicates significant stenosis
• Long exam — patient positioning is crucial

PSV >180 cm/s at renal artery origin + RAR >3.5 = significant stenosis. RI >0.8 = poor response to revascularization.