UltraRounds: Applicability of Renal Resistive Index in the Coronavirus Patient

What is the Renal Resistive Index? 

1. RRI is the sonographic Doppler measurement of flow velocities in the intraparenchymal renal arteries. It has been shown to correlate with renal vascular impedance. 
2. Generally, values above 0.7 are considered abnormal. Renal transplant patients with values above 0.8 are associated with higher mortality.  
3. Critically Ill COVID-19 patients with AKI have been shown to have a higher RRI than those without AKI. 

How is RRI calculated? 

1. Start with getting a long axis view of the kidney. 
2. Apply color doppler to identify pulsatile flow in the kidney. 
3. Place pulse wave doppler gate over the interlobar pulsatile vessels. 
4. Peak systolic velocity (PSV) and End diastolic velocity (EDV) are measured. 

RRI = PSV-EDV/PSV  

1. Values above 0.7 are considered abnormal.