Contrast Enhanced Sonography Shows Superior Microvascular Renal Allograft Perfusion in Patients Switched From Cyclosporine A to Everolimus

Background. Real-time contrast enhanced sonography (CES) provides quantitative information on microvascular tissue perfusion in renal allografts. In contrast to calcineurin inhibitors, mammalian target of rapamycin inhibitors may have beneficial effects on renal microvascular tissue perfusion. There is no information on the microperfusion of renal allografts in patients receiving either mammalian target of rapamycin inhibitor or calcineurin inhibitor. Methods. In a prospective randomized, clinical trial, renal parenchymal tissue perfusion of 24 stable renal allograft recipients was evaluated with CES. Eleven patients were kept on cyclosporine A (CsA); 13 were converted to everolimus (EVR). Measurements were made at the time of the switch from CsA to EVR, 8.21 +/- 6.36 months posttransplantation, and 21.2 +/- 6.57 months posttransplantation. In addition to laboratory and clinical parameters, Doppler indices and estimated glomerular filtration rate (eGFR) were measured. Results. After the switch from CsA to EVR, microvascular perfusion in the EVR-treated patients (A X beta value at baseline 9.23 +/- 7.44 dB/sec, A X beta value at time of follow-up 19.6 +/- 13.0 dB/sec, P = 0.03) and the estimated GFR (81.2 +/- 20.3 and 96.9 +/- 22.6 mL/min, P = 0.001) improved significantly. Microvascular perfusion (A X beta 7.04 +/- 5.32 dB/sec and A X beta 8.66 +/- 9.01 dB/sec, P = 0.34) and the eGFR of the group continuing CsA treatment remained stable (78.5 +/- 25.9 and 73.2 +/- 37.3 mL/min, P = 0.1). Conclusion. The Study demonstrates that renal microperfusion visualized by CES based on microbubble contrast agent and concomitantly kidney function, improved significantly after the switch from CsA to EVR.