No rise in renal Doppler resistance indices at peak serum levels of cyclosporin A in stable kidney transplant patients

Background. The measurement of intrarenal resistance indices by duplex ultrasound plays an important role in the follow-up care of renal transplant patients. Increasing resistance indices indicate rejection episodes, but may also occur e.g. in parenchymal renal diseases. As calcineurin inhibitors induce vasoconstriction both in vivo and in vitro, we studied whether peak serum levels of cyclosporin A led to an acute rise in renal resistance indices via the induction of intrarenal vasoconstriction. Methods. The acute impact of peak serum levels of cyclosporin A on intrarenal resistance indices was studied in 36 patients after allogeneic renal transplantation. All patients were transplanted for > 6 months and received an immunosuppressive treatment comprising cyclosporin A. Intrarenal resistance indices were measured by duplex ultrasound immediately before (trough serum level) and 2 h after (peak serum level) the oral intake of cyclosporin A at the individual maintenance dose. Results. Compared with renal resistance indices measured at trough serum levels [resistive index (RI) 0.72 +/- 0.07; pulsatility index (PI) 1.40 +/- 0.27], values remained unchanged at peak serum levels of cyclosporin A (RI 0.72 +/- 0.08; PI 1.43 +/- 0.31). Renal resistance indices correlated with the age of the patients, but not with mean arterial pressure or time since transplantation. Conclusions. The oral intake of cyclosporin A does not induce an acute rise in intrarenal resistance indices in stable transplanted patients. Thus, timing of duplex ultrasound examinations with regard to the intake of cyclosporin A is not necessary in these patients.