Doppler-based renal resistive index: Clinical and prognostic significance

Abstract

An increasing body of evidences suggests that renal Doppler may help to assess perfusion of native or transplanted kidneys. Renal Doppler has been proven to be a valuable tool for assessing large arterial or venous abnormalities. The resistive index (RI) is a Doppler-derived parameter that is calculated as follows: RI = [peak systolic shift − minimum diastolic shift]/peak systolic shift. Renal RI has been shown to be correlated with renal arteriosclerosis and may help to assess prognosis, and even to tailor treatment, in hypertensive patients or those with diabetes mellitus. This parameter has also been evaluated in various renal diseases but seems to be an integrative parameter rather than a predictor of a specific event. Also, RI has been suggested for the early detection of acute kidney injury (AKI). However, numerous factors have been shown to influence RI, and this integrative parameter neither constitutes an alternative to renal biopsy nor provides valuable information on renal blood flow. Moreover, experience with RI in all these fields is scant, and our understanding of factors influencing RI is limited. Before implementing this technique in clinical practice, large, adequately powered studies conducted in unselected patients are warranted to better evaluate RI determinants and clinical significance.