A novel simple noninvasive index to predict renal transplant acute rejection by contrast-enhanced ultrasonography.

Purpose. This study aimed to evaluate the application of quantitative contrast-enhanced ultrasonography (CEUS) in the assessment of renal allograft dysfunction and to establish a new noninvasive index to predict acute rejection (AR). Methods. Fifty-seven renal transplant recipients were enrolled in this prospective study. Before renal allograft biopsy, CEUS examinations were performed. The biopsy results proved 23 cases of AR (AR group), 10 cases of acute tubular necrosis (ATN group), and 24 with normal evolution (stable group). Contrast-enhanced ultrasonography parameters including rising time (RT), time to peak (TTP), and the delta-time among regions of interest (Delta RT and Delta TTP) were analyzed. Results. In the AR group, RT and TTP of interlobar artery and medulla (RTi, RTm, TTPi, and TTPm) as well was Delta RT and Delta TTP between medulla and cortex (Delta RTm-c and Delta TTPm-c) were significantly higher compared with those in the stable group. RTm and TTPm as well as Delta RTm-c and Delta TTPm-c were remarkably higher compared with those in the ATN group. Delta RTm-c and estimated glomerular filtration rate (eGFR) were identified as independent predictors by multivariate analysis (P = 0.008 and P = 0.024). On the basis of the multivariate analysis results and area under the receiver operating characteristic curves of individual markers, we constructed a new simple index, P = -0.587 + 0.286 x Delta RTm-c - 0.028 x eGFR; new index = e(P)/(1 + e(P)), to discriminate AR, which had better area under the receiver operating characteristic curves than eGFR or individual CEUS parameters. Conclusion. Contrast-enhanced ultrasonography parameters are reliable markers for differentiating the perfusion status of transplanted kidneys. Furthermore, the new simple index can easily predict AR with a high degree of accuracy.