Renal functional reserve in patients with a reduced number of functioning glomeruli

Renal functional reserve (RFR) has been reported to be either reduced or absent in patients with renal insufficiency. Our study consisted in measuring RFR by acute protein load (PL) in 3 groups of patients: the first one was composed of 20 patients (pts) with biopsy-proven glomerular disease (GN) and a varying percentage of sclerotic glomeruli (15-70%); the second one consisted of 10 patients with acquired single kidney (SK) and the third group contained 5 patients with surgical ablation of more than 50% renal tissue (LRRM). Twenty-four healthy volunteers were studied as control subjects. The GFR percentage increase (delta GFR%) after PL in CS did not differ from that of the three groups of patients, despite a significant difference in resting GFR (CS = 113 +/- 11 ml/min/1.73 m2: GN 72 +/- 28 ml/min/1.7, p less than 0.01 vs CS; SK 81 +/- 20 ml/min/1.73 m2, p less than 0.01 vs CS; LRRM 45 +/- 10 ml/min/1.7, p less than 0.01 vs CS; Moreover, an inverse correlation was not found either between GFR and the percentage of sclerotic glomeruli in GN (r = 0.01, p = NS) or between GFR and the extent of excised renal tissue in the other two groups (r = 0.38, p = NS). In conclusion, our data do not confirm that RFR is necessarily reduced or absent in patients with a reduced number of functioning glomeruli, nor do they uphold the hypothesis of constant hyperfiltration in the remaining glomeruli.