Renal Resistive Index

RRI is derived from blood-flow velocities measured in interlobar arteries within the renal parenchyma. RRI correlates with renal vascular resistance, renal vascular compliance, and systemic haemodynamics. RRI is affected by systemic factors as well as intrinsic renal vascular tone. Age, diabetes, and hypertension can affect RRI by changing endothelial integrity and vessel wall properties. RRI is a non-invasive Doppler ultrasound measure of intrarenal vascular haemodynamics.