Kidneys in the Crossfire: Insights into Renal Sarcoidosis

Background: Renal Sarcoidosis is rare with an uncertain incidence and prevalence due to disease heterogeneity. It typically manifests with nephrocalcinosis and glomerular lesions, however, can vary. We aim to evaluate renal sarcoidosis and explore outcomes through a retrospective analysis at a tertiary centre in Manchester, UK. Methods: A retrospective observational study with biopsy-proven kidney disease (KD) in Sarcoidosis, assessing demographics, presentation, histology, management, and outcomes over a median follow-up of 6 years. Adverse renal outcome (AO), progression to CKD 4 or 5 or requiring dialysis was the primary outcome. Univariate comparisons and regression analyses were used to identify predictors of poor outcome. Results: Of the 32 patients, 44% presented with KD. In others, KD was noted on average 2.5 years after non-renal Sarcoidosis. 9 patients experienced AO; most were younger at presentation compared to the non-OA group (49.2 vs 61.8 years, p=0.041). There was no significant difference in sex, prior diagnosis, or multi-organ involvement. Granulomatous interstitial nephritis was the most common histology (55.6% vs 56.5%). Steroids were used in 78.1% of patients, predominantly prednisolone; 56% received high-dose regimen (≥30 mg/day). Patients with AO had lower eGFR at presentation (~20 vs 50 mL/min, p=0.04). By 100 months, 25% of patients relapsed, 4 progressed to ESKD and 3 died. Conclusion: Renal sarcoidosis, is associated with adverse outcomes, and a return to baseline renal function is often not achieved. Aside from younger age and lower eGFR at presentation, there are no clear predictors of poor outcomes. Relapse rate and progression to ESKD highlight the need for proactive management. Prospective, multicentre studies are needed to refine prognostic tools and guide long-term care.