A novel approach to the histological diagnosis of pediatric nephrotic syndrome by low vacuum scanning electron microscopy.

Despite intensive treatment, steroid-resistant nephrotic syndrome (NS) often progresses to endstage renal disease. Therefore, a more accurate and quick histological diagnosis is required to properly treat such patients. The aim of this study was to introduce a novel approach to the histological diagnosis of pediatric NS by low vacuum scanning electron microscopy (LVSEM) and to describe the morphological differences in glomeruli between steroid-sensitive and steroid-resistant NS specimens. The subjects were three patients with steroid-sensitive NS and four patients with steroid-resistant NS. Conventional renal biopsy paraffin sections were stained with platinum-blue (Pt-blue) or periodic acid methenamine silver (PAM) and directly observed under LVSEM at magnifications between ×50 and ×10,000. The Pt-blue-stained sections showed three-dimensional structural alterations in glomerular podocytes and foot processes. PAM-stained sections showed changes in the structure and thickness of the glomerular basement membrane (GBM). Consequently, many round-shaped podocytes and elongated primary foot processes were exclusively recognized in steroid-resistant NS, although irregularities in foot process interdigitation, fusions, effacements, and microvillus transformations were observed in both steroid-sensitive and steroidresistant NS. Irregularities in thickness and the wrinkling of GBMs were clearly detected in steroid-resistant NS. The evaluation by LVSEM is probably useful for the renal histological diagnosis of pediatric NS.