Intrarenal vascular resistance parameters in kidney transplant patients receiving calcineurin inhibitor-based or sirolimus-based regimens.

Background: Use of a calcineurin inhibitor (CNI) immunosuppressant following kidney transplantation is associated with development of vasomotor nephrotoxicity. This study was undertaken to evaluate and compare the influences of CNI-based and CNI-free immunosuppressant regimens on two intrarenal vascular resistance parameters, the resistive index (RI) and the pulsatility index (PI), in renal transplant recipients.

Methods: Forty-nine renal transplant patients who received ultrasonography examination between January 2007 and December 2007 were enrolled in this case-control study. Thirty-one subjects received a CNI-based regimen, and 18 received a CNI-free (sirolimus-based) regimen. RI and PI were determined by duplex Doppler ultrasonography.

Results: Patients receiving a CNI displayed lower cholesterol and triglyceride values and higher RI (mean: 0.7 vs. 0.6, P = 0.002) and PI values (mean: 1.3 vs. 1.1, P = 0.034). Multivariate analyses revealed that advanced age and use of alpha-blockers or diuretics were modestly associated with higher RI and PI values. By multivariate analysis, use of sirolimus was associated with a lower RI by -0.05 [95% confidence interval (CI): -0.085, -0.019; P = 0.003] but not with a lower PI (95% CI: -0.245, 0.001; P = 0.053).

Conclusions: Use of sirolimus is only modestly correlated with a reduced RI and is not associated with a reduced PI. These observations question the superiority of CNI-free over CNI-based regimens with regard to reduction of intrarenal vascular resistance post-transplantation. These findings combined with those regarding recipient factors also cast doubt on the specificity of intrarenal resistance indices for predicting allograft function and/or survival.