Contrast-Enhanced Ultrasonography in the Early Period After Kidney Transplantation Predicts Long-Term Allograft Function

Introduction. Real-time contrast-enhanced sonography (CBS) can assess microvascular tissue perfusion using gas-filled microbubbles. The purpose of the study was to evaluate the feasibility of early CBS in predicting long-term kidney allograft function in comparison to color Doppler ultrasonography (CDUS). Methods. We prospectively studied 68 consecutive kidney transplant recipients using CBS and conventional CDUS investigation 1 week after transplantation. Transplant tissue perfusion imaging was performed by low-power imaging during intravenous administration of the sonocontrast SonoVue. Renal tissue perfusion was assessed quantitatively using flash replenishment kinetics of microbubbles to estimate renal blood flow (RBF). The obtained sonography values were correlated with clinical data 1 week up to 1 year after transplantation. Results. In contrast with conventional CDUS resistive indices, RBF estimated by CBS 1 week posttransplantation significantly correlated with kidney function after 1 year (r = 0.67; P < .001). Determination of RBF by CBS revealed a significant correlation with donor age but not recipient age, whereas conventional CDUS resistive index was significantly correlated to recipient age (r = 0.54; P < .001) but not donor age. Furthermore RBF was associated with vascular fibrosis and intimal thickening of the engraftment biopsies. Conclusion. This is the first prospective study demonstrating the prognostic value of CES early after kidney transplantation. In contrast with CDUS, CBS reveals information about kidney allograft perfusion independent of recipient vascular compliance.