Non-diabetic Kidney Disease in Type 2 Diabetes: From Kidney Biopsy to Precision Medicine

Non-diabetic kidney disease (NDKD) is increasingly recognized as a significant and often underappreciated problem in people with type 2 diabetes mellitus (T2DM), accounting for a substantial proportion of kidney abnormalities identified through biopsy. Recent evidence shows that many patients do not have purely diabetic kidney changes; instead, a large share have non-diabetic or mixed pathologies. These findings challenge the long-standing assumption that kidney disease in diabetes is always due to diabetic nephropathy. This narrative review synthesizes current evidence on the prevalence, clinical predictors, diagnostic tools, and therapeutic strategies for NDKD in T2DM, with a focus on combining renoprotective therapy with disease-specific immunomodulation. We reviewed PubMed, EMBASE, and Scopus (January 2020-December 2024), including systematic reviews, meta-analyses, randomized controlled trials, cohort studies, and clinical guidelines, addressing NDKD in diabetes. NDKD shows substantial geographic variation. IgA nephropathy (IgAN) is most common in Asian cohorts (25%-43%), whereas membranous nephropathy (MN, 20%-30%) and focal segmental glomerulosclerosis (FSGS, 18%-25%) predominate in Western populations. Key clinical predictors include the absence of diabetic retinopathy (odds ratio (OR) 0.15, 95% confidence interval (CI) 0.09-0.26 for DKD), diabetes duration under five years (OR 5.8, 95% CI 3.2-10.5 for NDKD), hematuria (OR 7.2, 95% CI 4.1-12.6), and rapid estimated glomerular filtration rate (eGFR) decline greater than 5 mL/min/1.73 m² per year (OR 4.3, 95% CI 2.8-6.7). Prediction models report areas under the curve (AUC) of 0.82-0.89. Emerging tools, including urinary proteomic panels (AUC 0.88-0.91) and artificial intelligence (AI)-assisted histopathology (AUC 0.91), are promising but do not replace kidney biopsy. Renoprotective therapies remain essential. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) show hazard ratios (HR) of 0.61-0.72 for kidney outcomes; glucagon-like peptide-1 receptor agonists (GLP-1 RA) around 0.76; and mineralocorticoid receptor antagonists (MRA) about 0.82. Disease-specific immunomodulation is equally important, including rituximab for MN (HR 3.82, 95% CI 2.42-6.02) and complement-targeting therapies for IgAN. NDKD requires integrated management that combines standard renoprotection (SGLT2i, renin-angiotensin system (RAS) blockade, GLP-1 RA, MRA) with histology-guided immunosuppression. Kidney biopsy should be pursued when results are expected to change management decisions. Overall, NDKD affects one-third to one-half of patients with T2DM and kidney disease. Early recognition, maintaining clinical suspicion in patients with atypical features, appropriate biopsy use, and tailored treatment strategies are essential to improving outcomes.