Ultrasound measurement of change in kidney volume is a sensitive indicator of severity of renal parenchymal injury

Non-invasive determination of the severity of parenchymal injury in acute kidney injury (AKI) remains challenging. Edema is an early pathological process following injury, which may correlate with changes in kidney volume. The goal of this study was to test the hypothesis that 'increases in kidney volume, measured in vivo using ultrasound correlate with the degree of renal parenchymal injury'. Ischemia reperfusion (IR) of varying length was utilized to produce graded tissue injury. We first determined 1) whether regional kidney volume in rats varied with the severity (0, 15, 30, 45 minutes) of warm bilateral IR and 2) whether this correlated with tubular injury score. We then determined whether these changes could be measured in vivo using 3D ultrasound. Finally, we evaluated cumulative changes in kidney volume up to 14 days post-IR in rats to determine whether changes in renal volume were predictive of latent tubular injury following recovery of filtration. Studies concluded that non-invasive ultrasound measurements of change in kidney volume over 2 weeks are predictive of tubular injury following IR even in animals in which plasma creatinine was not elevated. We conclude that ultrasound measurements of volume are a sensitive, non-invasive marker of tissue injury in rats and that the use of 3D-ultrasound measurements may provide useful information regarding the timing, severity and recovery from renal tissue injury in experimental studies.