Renal arterial resistive index

The renal arterial resistive index (RI) is a sonographic index to assess for renal arterial disease.

It is measured as 

RI = (peak systolic velocity - end diastolic velocity ) / peak systolic velocity

  • the normal value is ≈ 0.60
  • with 0.70 being around the upper limits of normal


Measured at arcuate arteries (at the corticomedullary junction) or interlobar arteries (adjacent to medullary pyramids)

Reasons for elevated values
Reasons for elevated values in a transplant kidney

There is thought to be little correlation between the RI and the quantitative extent of renal dysfunction (measured by serum creatinine values) 2.

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