Renal resistive indexes: variability in Doppler US measurement in a healthy population

Radiology. 1996 Apr;199(1):165-9. doi: 10.1148/radiology.199.1.8633141.


Purpose: To determine the variability in resistive index (RI) in normal kidneys, possible causes of variability, and consequences of reporting a single value.

Materials and methods: Doppler ultrasound RI measurements were obtained in the upper, middle, and lower regions of 118 kidneys in 58 healthy subjects (aged 24-70 years; 35 women, 23 men) who subsequently underwent angiography. The effects of sampling a particular parenchymal region, vascular territory, or kidney were assessed.

Results: Kidney region, vascular territory, and right versus left kidney had no consistently significant effect (P < or = .05) on RI. Age had a statistically significant effect. RI readings were highly correlated with each other both within a subject and within a kidney. The probability that a single RI value would exceed 0.70 in a healthy 45-year-old subject was 6%; this decreased to 3% when three readings were averaged.

Conclusion: The variability of RI measurements in a kidney suggests that a number of RI readings should be averaged before a single representative value is reported.

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Analysis of Variance
  • Female
  • Humans
  • Kidney / blood supply
  • Kidney / diagnostic imaging*
  • Linear Models
  • Male
  • Middle Aged
  • Reference Values
  • Renal Circulation / physiology*
  • Ultrasonography, Doppler
  • Vascular Resistance / physiology