Renal function reserve in stable grafts and its relationship to renal morphologic parameters

Cyclosporine-a-based immunosuppression and renal functional reserve in organ-transplant patients

The glomerular filtration rate (GFR) may increase after oral protein overload or after an amino acid infusion. Renal functional reserve (RFR) is defined as the difference between the poststimulation and the baseline glomerular filtration rate. RFR has been studied in transplant patients. The results have been conflicting because RFR may be affected by donor age, the time from transplantation, the type of immunosuppression, the basal GFR, the body surface area, and the presence of calcium channel blocker therapy. We observed that during the first year posttransplantation renal recipients maintained on cyclosporine (CsA) therapy retain a level of RFR that represents approximately 30% of the baseline GFR. Moreover, hypertensive cyclosporine treated renal transplant patients on calcium channel blocker therapy do not exhibit permanent glomerular hyperfiltration until 8 months posttransplantation. Finally, both renal and heart transplant patients on cyclosporine therapy possess renal reserve, but the single renal graft in renal transplant patients shows a proportionally higher baseline GFR and a better ability to exhibit a RFR than the two native kidneys in heart transplant patients. Many studies, although not all, have documented a positive RFR in both children and adult cyclosporine-treated kidney graft recipients, demonstrating that hyperfiltration is not the rule following single kidney transplantation.

Contrast-enhanced sonography of the renal transplant using triggered pulse-inversion imaging: preliminary results

The purpose of our study was to quantify renal transplant parenchymal sonographic enhancement using pulse-inversion imaging (PII) and intermittent emission after contrast administration by means of bolus and infusion techniques, and to evaluate renal perfusion functional indices. A total of 34 patients, presenting with minor abnormalities (n = 14) and cortical perfusion changes due to parenchymal disorders (n = 12) or renal artery stenosis (n = 8) were included. Cardiac-triggered contrast-enhanced PII ultrasound (US) was performed after administration of SHU 508 A (Schering AG, Berlin, Germany), using a high mechanical index, a frame rate of one image every four cardiac cycles for bolus study, and a decreasing frame rate for infusion study. Compared to baseline values, peak enhancement ratio ranged from 5.6 to 14.7 using a bolus administration, and reached a value of 2.1 to 4.0 using infusion technique. Qualitative analysis showed heterogeneous enhancement in most allografts presenting with acute parenchymal disease (p = 0.03). In bolus studies, time to peak, wash-in and wash-out slopes increased in renal transplants with parenchymal disease and renal artery stenosis (p = 0.0001). Infusion administration exhibited no plateau in signal level, and no significant difference in enhancement ratio was found between groups of patients. Triggered PII after contrast agent administration provides morphologic and quantitative information about cortical vascularity in renal transplants.