This article states that the 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.

This index has a relatively recent history and an unfortunate name: resistance index (or resistive index). It was initially proposed by Gosling and King2 and Pourcelot3 in 1974 to identify the renal vascular diseases through the noninvasive measurement of intrarenal hemodynamics indirectly related to changes in arteriolar resistance.

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