Biopsy-Proven Glomerular Diseases in Saudi Arabia: The Clinicopathological Spectrum and Predictors of Renal Outcomes in a Single-Center Cohort and Four Decades of National Data

Background Glomerular diseases are a significant contributor to chronic kidney disease (CKD) in Saudi Arabia. Local data linking biopsy findings to renal outcomes are scarce, and the available series are mostly descriptive. Objectives The objective of this study is to characterize the clinicopathological spectrum of biopsy-proven glomerular disease at a single Saudi tertiary center, identify histological and clinical predictors of renal function decline at one year, and secondarily compare these findings descriptively with previously published Saudi biopsy series. Methods We retrospectively reviewed native kidney biopsies performed over a 24-year period. The primary outcome was a composite renal endpoint at one year (≥ 40% decline in eGFR or eGFR < 15 mL/min/1.73 m²), with sensitivity analyses using a 30% decline threshold. Predictors were assessed by multivariable logistic regression in a complete-case cohort of 289 patients. Results Of 700 biopsies screened, 333 met the inclusion criteria. The most common diagnoses were lupus nephritis (72; 21.6%), followed by focal segmental glomerulosclerosis (FSGS) (60; 18%), diabetic nephropathy (46; 13.8%), and IgA nephropathy (35; 10.5%). FSGS was the most common primary glomerular lesion, and lupus nephritis was the leading secondary diagnosis. Overall, 124 of 314 patients with follow-up (39%) reached the composite outcome at one year. Moderate to severe interstitial fibrosis and tubular atrophy (IFTA) (aOR 2.13, 95% CI 1.14-3.98; p = 0.018) and moderate to severe arteriosclerosis (aOR 2.38, 95% CI 1.09-5.26; p = 0.034) independently predicted the outcome, as did higher 24-hour urinary protein (aOR 1.08 per g/day, 95% CI 1.01-1.15; p = 0.026) and lower baseline eGFR (aOR 0.98 per mL/min/1.73 m², 95% CI 0.97-0.99; p < 0.001). Conclusion In this 24-year biopsy cohort, chronic histopathological damage was an independent predictor of renal function decline at one year, alongside proteinuria and baseline eGFR. These findings show that chronicity on biopsy carries prognostic weight and support the need for dedicated national glomerulonephritis (GN) registries combining histopathological findings with longitudinal follow-up.