Real-time contrast-enhanced sonography of renal transplant recipients predicts chronic allograft nephropathy.

Real-time contrast-enhanced sonography (RT-CES) can assess microvascular tissue perfusion using gas-filled microbubbles. The study was performed to evaluate the feasibility of RT-CES in detecting chronic allograft nephropathy (CAN) in comparison to color Doppler ultrasonography (CDUS). A total of 26 consecutive renal transplant recipients were prospectively studied using RT-CES and conventional CDUS. Transplant tissue perfusion imaging was performed by low-power imaging during i.v. administration of the sonocontrast Optison. Renal tissue perfusion was assessed quantitatively using flash replenishment kinetics of microbubbles to estimate renal blood flow A *beta (A = peak signal intensity, beta= slope of signal intensity rise). In contrast to conventional CDUS resistance and pulsatility indices, renal blood flow estimated by CES was highly significant related to S-creatinine (r =-0.62, p = 0.0004). Determination of renal blood flow by CES reached a higher sensitivity (91% vs. 82%, p < 0.05), specificity (82% vs. 64%, p < 0.05) and accuracy (85% vs. 73%, p < 0.05) for the diagnosis of CAN as compared to conventional CDUS resistance indices. Perfusion parameters derived from RT-CES significantly improve the early detection of CAN compared to conventional CDUS. RT-CES using low-power real-time perfusion imaging is a feasible method to evaluate microvascular perfusion in renal allograft recipients.