Estimation of Total Glomerular Number in Stable Renal Transplants

Abstract

ABSTRACT. Glomerular number (Ng) is considered a major determinant of renal function and outcome. In the dog, it has been shown that Ng can be estimated with reasonable precisionin vivoby means of a renal biopsy and magnetic resonance imaging (MRI). Thus, this method was applied to study anatomoclinical correlations in stable human renal transplants. Thirty-nine stable renal transplants were included. A protocol renal allograft biopsy was done at 4 mo. Biopsies were evaluated according to Banff criteria. Glomerular volume fraction (Vvglom/cortex) was measured by means of a point-counting method, and mean glomerular volume (Vg) was estimated by means of Weibel and Gomez (Vg-W&G) and maximal profile area (Vg-MPA) methods. MRI was used to estimate renal cortical volume (Vcortex). Ngwas calculated as (Vvglom/cortex× Vcortex)/Vg. GFR was estimated by the inulin clearance. Ten age-matched donor biopsies served as controls for Vg. Histologic diagnosis was as follows: normal (n= 20), borderline (n= 7), acute rejection (n= 1), and chronic allograft nephropathy (n= 11). Vvglom/cortexwas 3.4 ± 1.1%, Vcortexwas 167 ± 46 cm3, Vg-W&G was 3.2 ± 1.2 × 106μm3, and Vg-MPA was 3.3 ± 1.0 × 106μm3. Vg-W&G in donor and recipient biopsies was not different (3.6 ± 1.1versus3.2 ± 1.2 × 106μm3). Total glomerular number estimated by means of Vg-W&G (Ng-W&G) was 0.73 ± 0.33 × 106and by Vg-MPA (Ng-MPA) was 0.74 ± 0.31 × 106. A positive correlation between GFR and Ng-W&G (r= 0.47,P= 0.002) was observed. Furthermore, the older the donor, the higher Vg-W&G (r= 0.37,P= 0.01) and the lower Ng-W&G (r= −0.40,P= 0.01). Total glomerular number can be estimated in stable renal allografts by means of a renal biopsy and MRI. Our data show that Ngdepends on donor age and positively correlates with GFR. E-mail: 28383xfo@comb.es