The Characteristics of Renal Microperfusion in Acute Kidney Injury: Initial Experience with Quantitative Contrast-Enhanced Ultrasound

Abstract This study aimed to assess use of contrast-enhanced ultrasonography (CEUS) in evaluating patients with acute kidney injury (AKI) and investigate its correlationwith renal pathology and clinical outcomes. 16 patients with AKI induced by tubulointerstitial nephritis and 12 volunteers. CEUS parameters, including peak intensity (PI), rise time (RT), time to peak (TTP), mean transit time (mTT), and their cortex-to-medulla ratio, were compared within AKI subgroups and the control group. The relationship of these parameters with renal pathology and renal outcome was analyzed. The cortex-to-medulla PI ratio of AKI showed a decrease, indicating the presence of medullary congestion. In patients with AKI stage 3, the cortex-to-medulla PI ratio showed positive correlation with the glomerular sclerosis score(r=0.690). Additionally, the score for chronic tubulointerstitial injury had negative correlations with cortical RT and cortical TTP (r=-0.807 and r=-0.821), and their cortex-to-medulla ratios (r=-0.576 and r=-0.547), while having a positive correlation with cortex-to-medulla PI ratio (r=-0.501). 14 patients underwent a 3-month follow-up. Subsequent comparison disclosed that a lower PI ratio was closely related to a more favorable renal outcome. We found CEUS enables the detection of renal perfusion redistribution in AKI, and a reduced cortex-to-medulla PI ratio suggests medullary congestion. The cortex-to-medulla PI ratio holds potential as a prognostic indicator for AKI, contributing to both diagnosis and the prediction of renal outcomes.