The “Renocentric Theory” of Renal Resistive Index: Is It Time for a Copernican Revolution?

Ultrasound (US) with duplex Doppler scanning has spread to the capillary level, becoming an irreplaceable tool in daily clinical practice thanks to its characteristics: low cost, repeatability, and noninvasiveness. Moreover, US has become over time more sensitive and accurate; it can be considered an extension of the clinician’s hand. For this reason, it currently represents the ideal tool for first-level diagnostic use in several fields, and is the simplest and most flexible instrument for obtaining morphological and functional information on different organs, including the kidneys. In this issue of The Journal, Gigante, et al1 propose to assess renal involvement in patients with systemic sclerosis (SSc) through the evaluation of both structural and hemodynamic US measurements, paying particular attention to the Doppler-measured renal resistive index (RRI) and its clinical significance.