Diagnostic role of electron microscopy in native kidney biopsies: a 10-year study

Abstract Background Kidney diseases exhibit substantial clinical and pathological heterogeneity, making a multimodal diagnostic approach essential for accurate classification and treatment planning. This study aims to evaluate the true diagnostic contribution of electron microscopy in native kidney biopsies by correlating ultrastructural findings with clinical, histopathological, and biochemical parameters. Methods Kidney biopsy specimens obtained for clinical indications at Mersin University Faculty of Medicine between 2013 and 2022 were retrospectively reviewed. During this period, all native kidney biopsies were routinely evaluated by light microscopy, immunofluorescence, and electron microscopy. Of 1360 biopsies received, 729 adult native kidney biopsies met the inclusion criteria. The diagnostic contribution of electron microscopy was classified as essential/critical, supportive, or non-contributory, acknowledging its role in refining diagnostic interpretation. Associations of electron microscopy findings with pathological and biochemical variables were also analyzed. Results Among 729 biopsies, the most frequent diagnoses were membranous nephropathy (17.4%), IgA nephropathy (15.6%), and diabetic nephropathy (15.2%). Electron microscopy was essential/critical in 20.7%, supportive in 67.5%, and non-­contributory in 11.8% of cases. Notably, electron microscopy identified electron-dense deposits in 64.0% of immunofluorescence-negative and 92.9% of technically inadequate immunofluorescence cases, highlighting its diagnostic value when immunofluorescence findings were limited. Ultrastructural abnormalities correlated strongly with immunofluorescence patterns and proteinuria severity. Conclusions Electron microscopy provides clinically meaningful diagnostic information by refining kidney biopsy interpretation beyond light microscopy and immunofluorescence, particularly through improved localization of immune deposits and detection of deposits in immunofluorescence limited cases. Its integration with light microscopy and immunofluorescence supports more accurate and comprehensive diagnosis.