Histopathology of Diabetic Nephropathy: Beyond Glomerular Basement Membrane Thickening

Diabetic nephropathy (DN) is a leading cause of chronic kidney disease and end-stage renal disease worldwide, characterized by progressive injury across all renal compartments. Traditionally considered a glomerular disorder marked by basement membrane thickening, mesangial expansion, and nodular sclerosis, DN is now recognized as a multifaceted process involving tubulointerstitial, vascular, and podocyte pathology. This narrative review integrates current histopathological insights, highlighting key glomerular lesions, tubular basement membrane thickening, interstitial fibrosis, arteriolar hyalinosis, and podocyte injury, as well as atypical and advanced patterns. The role of kidney biopsy in diagnosis, the application of the Renal Pathology Society classification, and differentiation from mimicking conditions such as amyloidosis and monoclonal deposition disease are discussed. Emerging biomarkers and advanced imaging modalities offer promise for earlier detection and risk stratification. Understanding the full histological spectrum of DN is critical for accurate diagnosis, prognostication, and the development of targeted therapies. Future directions include molecular classification, non-invasive diagnostics, and precision medicine approaches to improve patient outcomes.