Resistive Index or color-Doppler semi-quantitative evaluation of renal perfusion by inexperienced physicians: results of a pilot study

Background. Doppler-based renal resistive index (RI) calculation may help in the early detection of acute kidney injury (AKI). Its feasibility and reproducibility by inexperienced operators remain unknown. The main objective of this study was to compare performances of junior and senior operators in assessing renal perfusion using both the semiquantitative color-Doppler scale and RI calculation. Methods. Prospective cohort study performed in 3 ICUs. Inexperienced juniors physicians attended a half-day course on renal perfusion assessment using RI calculation and color-Doppler (from 0, absence of renal perfusion; to 3, renal vessels identifiable in the entire field of view). Junior and senior operators used both methods in 69 mechanically ventilated patients, in blind fashion. Results. Failure to obtain RI occurred for a junior operator in a single patient. RI and color-Doppler semi-quantitative values obtained by operators were correlated (r(2)=0.64 and r(2)=0.61, respectively). Systematic bias across operators as assessed using Bland-Altman plots was negligible (-0.001 and -0.29, respectively), although precision was limited (95% confidence intervals, +0.105 to -0.107 and +0.98 to -1.04, respectively). RI calculation and semi-quantitative assessment performed well for diagnosing persistent AKI (area under the receiver-operating characteristic curve, 0.84 [95% confidence interval, 0.73-0.97] and 0.87 [0.77-0.97], respectively). Conclusion. A brief course on renal Doppler allowed inexperienced operators to assess effectively renal perfusion with a good reliability when compared to senior operators. In addition, our results suggest the good diagnostic performance of both Doppler-based RI and semi-quantitative renal perfusion assessment in predicting short-term renal dysfunction reversibility.