Background Lupus nephritis (LN) affects up to 60% of patients with systemic lupus erythematosus (SLE), either as the initial manifestation or during the disease course. Moreover, LN has a negative impact on survival of SLE patients. Accordingly, it is mandatory to identify specific and feasible markers able to guide clinicians towards the adequate therapeutic option in LN patients. Recently, a significant correlation between pathologic Resistive Index (RI) and class IV nephritis was identified, suggesting a role for RI as a severity marker.
Objectives We aimed at evaluating the role of RI as a marker of activity in a large cohort of LN patients.
Methods Consecutive patients with SLE who required a kidney biopsy were enrolled. SLE patients with known renal artery stenosis, heart failure, hepatic diseases and urinary tract obstruction were excluded. Functional renal evaluation was performed by assessing serum creatinine (mg/dL), blood urea nitrogen (BUN, mg/dL) and daily urinary protein excretion (g/24 h). Moreover, the estimated glomerular filtration rate (eGFR, mL/min) was assessed by using the formula developed by the Modification of Diet in Renal Disease Study. Immediately before renal biopsy, the ultrasonography evaluation was performed to assess RI (Aplio Ultrasound System SSA-790; convex probe 3.5-MHz, Toshiba, Tokyo, Japan). An RI value >0.7 was considered pathologic. The histologic characteristics of each kidney biopsy were registered in accordance with the International Society of Nephrology/Renal Pathology (ISN/RPS) Classification. Finally, biopsy-based activity (range: 0–24) and chronicity (range: 0–12) indices were calculated.
Results Sixty patients (M/F 4/56; mean age 35.3±11.3 years; mean disease duration 150.0±90.0 months) underwent kidney biopsy. According with ISN/RPS classification, 29 (48.3%) patients had a class IV, 17 (28.3%) a class III, 8 (13.4%) a class II, and 6 (10.0%) a class V LN. Seven patients (11.7%) showed an RI>0.7: one had a class III and 6/7 (85.7%) had a class IV. The evaluation of the activity index demonstrated the presence of significant higher values in patients with an RI>0.7 compared with those with normal RI values (8.6±5.0 versus 4.2±3.9; P=0.03). Moreover, RI values significantly correlated with age (P=0.01; R=0.3), creatinine levels (P=0.005; R=0.3), BUN (P=0.02; R=0.2), and eGFR (P=0.006; R=-0.3).
Conclusions In the present study, a significant association between pathologic RI and histological activity index in LN patients was found. In addition, we identified an association between pathological RI and a more severe kidney involvement suggesting a role of RI as an activity and severity marker of LN.
Disclosure of Interest None declared