Disease category Duplex criteria
Normal (0% DR)
  • PSV <180 cm/sec
  • No focal renal artery velocity increase
  • No poststenotic flow disturbance
  • RAR <3.5
Low-grade (1-59% DR)
  • PSV ≥180 cm/sec
  • Focal renal artery velocity increase
  • No poststenotic flow disturbance
  • RAR <3.5
High-grade (60-99% DR)
  • PSV ≥180 cm/sec
  • Focal renal artery velocity increase
  • Poststenotic turbulence
  • RAR ≥3.5
Total occlusion
  • No renal artery flow
  • Parenchymal velocity <10 cm/sec
  • Kidney length <9 cm
DR = diameter reduction; PSV = peak systolic velocity; RAR = renal-to-aortic velocity ratio.

Lourie J. Hemodynamic Parameters for Diagnosis of Advanced Renal Artery Stenosis by Duplex Ultrasound. The Journal of Vascular Technology 1994, 18 (2): pp 61-66.