The relationship between renal interstitial vasculopathy and clinical and prognosis of patients with lupus nephritis

Introduction: Renal vascular lesions (RVLs) are a common histopathological feature in lupus nephritis (LN). Despite their frequent occurrence, the clinical significance and prognostic impact of RVLs remain poorly understood. The main objectives of our study were to investigate the clinicopathological characteristics associated with RVLs in LN and to assess their prognostic implications in patients with LN. Methods: We conducted a retrospective analysis of baseline clinical and pathological data, as well as outcomes, for patients diagnosed with biopsy-confirmed lupus nephritis between September 1, 2008, and October 31, 2021. Patients were initially stratified into two groups based on the presence or absence of vascular disease at baseline. Subsequently, they were further categorized into four groups according to the severity of vascular disease. Comparisons were made across these groups with respect to clinical and laboratory parameters, pathological features, and prognostic outcomes. The composite endpoint was defined as death, end-stage renal disease (ESRD), or a ≥30% increase in serum creatinine. Survival analysis was performed using the Kaplan-Meier method to compare the renal survival and overall survival between groups with different severities of RVLs. The log-rank test was employed for univariate survival analysis, and multivariate analysis of survival outcomes was performed using the Cox regression model. Results: In a group of 225 patients, RVLs were found in 101 kidney biopsies, with 72 of these being mild. Among 156 patients with proliferative lupus nephritis, 77 had RVLs. Patients with RVLs were older and exhibited higher levels of serum creatinine, blood urea, uric acid, C-reactive protein, and significantly higher chronicity index and SLEDAI scores. They also had more severe tubulointerstitial lesions, worse clinical manifestations, and lower complete remission rates. Their estimated glomerular filtration rate was lower (p < 0.05). Compared to the NRVLs group, patients in the RVLs group had a lower renal survival rate and overall survival rate, and a significant difference was observed between the groups (p < 0.05). Importantly, the severity of vascular lesions was associated with a lower renal survival rate and overall survival rate, especially in proliferative lupus nephritis. Conclusion: RVLs are a common pathological feature in lupus nephritis and are particularly prevalent among patients with proliferative lupus nephritis. The presence and severity of RVLs are associated with more severe clinicopathological manifestations and a lower complete remission rate in lupus nephritis patients. Furthermore, they are predictive of poorer long-term outcomes, with a particularly pronounced impact on those with proliferative lupus nephritis.