Perfusion and T2 Relaxation Time as Predictors of Severity and Outcome in Sepsis‐Associated Acute Kidney Injury: A Preclinical MRI Study

Background Preventing sepsis‐associated acute kidney injury (S‐AKI) can be challenging because it develops rapidly and is often asymptomatic. Probability assessment of disease progression for therapeutic follow‐up and outcome are important to intervene and prevent further damage. Purpose To establish a noninvasive multiparametric MRI (mpMRI) tool, including T 1 , T 2 , and perfusion mapping, for probability assessment of the outcome of S‐AKI. Study Type Preclinical randomized prospective study. Animal Model One hundred and forty adult female SD rats (65 control and 75 sepsis). Field Strength/Sequence 9. 4T ; T 1 and perfusion map ( FAIR‐EPI ) and T 2 map (multiecho RARE ). Assessment Experiment 1: To identify renal injury in relation to sepsis severity, serum creatinine levels were determined (31 control and 35 sepsis). Experiment 2: Animals underwent mpMRI ( T 1 , T 2 , perfusion) 18 hours postsepsis. A subgroup of animals was immediately sacrificed for histology examination (nine control and seven sepsis). Result of mpMRI in follow‐up subgroup (25 control and 33 sepsis) was used to predict survival outcomes at 96 hours. Statistical Tests Mann–Whitney U test, Spearman/Pearson correlation ( r ), P < 0.05 was considered statistically significant. Results Severely ill septic animals exhibited significantly increased serum creatinine levels compared to controls (70 ± 30 vs. 34 ± 9 μmol/L, P < 0.0001). Cortical perfusion (480 ± 80 vs. 330 ± 140 mL/100 g tissue/min, P < 0.005), and cortical and medullary T 2 relaxation time constants were significantly reduced compared to controls (41 ± 4 vs. 37 ± 5 msec in cortex, P < 0.05, 52 ± 7 vs. 45 ± 6 msec in medulla, P < 0.05). The combination of cortical T 2 relaxation time constants and perfusion results at 18 hours could predict survival outcomes at 96 hours with high sensitivity (80%) and specificity (73%) (area under curve of ROC = 0.8, J max = 0.52). Data Conclusion This preclinical study suggests combined T 2 relaxation time and perfusion mapping as first line diagnostic tool for treatment planning. Level of Evidence 2 Technical Efficacy Stage 2