The application of the pop-off technique in the ultrastructural diagnosis of glomerular diseases.

Kidney glomerular diseases diagnosis is based on histological and ultrastructural investigations. Although the electron microscopy (EM) is essential for these diagnoses, the dedicated renal tissue for EM is not always available for various reasons. In 1981, the pop-off technique was used to recover samples from histological sections. Here, we show the application of the pop-off method to kidney biopsies for EM examination. Histological sections of kidney tissues fixed in Serra's solution, collected on untreated and treated glass slides and stained with H-E, PAS and Masson’s trichrome were recovered for EM through the pop-off technique. The measurement of glomerular basement membranes (GBM) thicknesses was carried out on renal tissues retrieved as well as on their counterpart conventionally fixed in glutaraldehyde. The pop-off method was successful performed on sections derived from different staining, storage times and microscope glass types. Tissue changes were noted and related to fixation, staining and recovering procedure. Ultrastructural analysis revealed an acceptable morphology in which parameters useful to diagnosis such as fusion of foot processes of the podocytes, presence of deposits and their localization as well as the GBM structures were identifiable. The comparative analysis performed on the same renal tissues processed through different procedures revealed a GBM thickness reduction in the retrieved samples. The pop-off technique represents a useful tool for recovering histological sections to be subjected to EM analysis. Despite some limitations, this technique can be applied to renal biopsies to rapidly provide ultrastructural diagnosis when the tissue is not available for EM.