Renal response to a protein load persists during long-term follow-up of children after renal transplantation

Background. Kidney donors and transplant recipients may be at risk of compl ications from glomerular hyperfiltration of the single kidney. It has been assumed that tests of the existence of renal functional reserve [Delta glom erular filtration rate (Delta GFR), Delta effective renal plasma flow (Delt a ERPF)] can be used to demonstrate hyperfiltration. It would therefore be of interest to evaluate the response of the kidney graft to a protein load, i.e,, testing the renal reserve and to find out whether a reduction in bas eline GFR is preceded by a loss of Delta GFR. Methods. We repeatedly studied the change in GFR and renal plasma flow (ERP F) after an oral protein load in 30 children after renal transplantation (T x), Follow-up time was 1.0-8.0 years, Renal function was evaluated with the clearances of inulin and para-aminohippuric acid (PAH). Seven recipient/do nor pairs were examined twice (median 0.3 and 4 years, after Tx). Results. The baseline GFR and ERPF remained stable throughout the follow-up and the increase after stimulation (Delta GFR and Delta ERPF) did not chan ge in the whole group of Tx children over the years. However, a reduction i n the baseline GFR from the first to the last investigation occurred in 23 of 30 children, In the 23 patients whose baseline GFR decreased, Delta GFR was still preserved, In the recipient/donor pairs, the baseline GFR and ERP F were the same, but on the second investigation, donors showed higher Delt a GFR. Conclusion. Despite fairly low baseline GFR and ERPF values in the Tx child ren, no change occurs in the capacity to increase GFR and ERPF after a prot ein load during follow-up, which suggests that they are not maximally hyper filtrating.