The cortical distribution pattern of diabetic glomerulopathy

In advanced diabetic nephropathy, all nephrons are affected. However, glomerulopathy shows some variation in severity. The aim of this study was to see whether the distribution of glomerular lesions bears any relationship to known renal anatomical/functional organization. Autopsy material from 12 long-term Type 1 (insulin-dependent) diabetic patients was collected retrospectively. Sections presenting the whole depth of cortex were subdivided into 3 zones of equal width. Two parameters were estimated in the deep and the superficial zones separately: in open glomeruli, the volume of red-stained (PAS-positive) material as a fraction of the total glomerular volume, and the number of occluded glomeruli as a fraction of the total number. The results show that the volume fraction of red-stained (PAS-positive) material, as well as the frequency of occluded glomeruli, are similar in the superficial and the deep zone. In addition, the spatial distribution of occluded glomeruli was tested for randomness. The occluded glomeruli are not randomly distributed, but show clustering. Furthermore, they tend to be located in columns perpendicular to the kidney surface, a tendency which cannot be explained by the general tendency for glomeruli to show such an arrangement. We conclude that it is unlikely that the combined structural and functional differences that exist between the superficial and deep glomeruli play a major role in the development of diabetic glomerulopathy. The kidney topology influences the process of glomerular occlusion. Several a priori, plausible mechanisms for the process are discussed.