Assessment of utility of renal resistive index as non-invasive radiological marker in patients with lupus nephritis

Background. Lupus nephritis is a common complication of systemic lupus erythematosus. Renal biopsy is the gold standard for diagnosing lupus nephritis. However, in recent years, the indications for renal biopsy in patients with systemic lupus erythematosus have been widely debated. Aim. To determine whether the use of color Doppler to measure the resistive index (RI) correlates with pathological findings in patients with lupus nephritis. Methods. We recruited patients into three groups: twenty-five adult patients with lupus nephritis as Group I, twenty-five SLE patients without nephritis as Group II, and twenty-five healthy volunteers as the control group. All participants underwent color Doppler examination to measure the renal resistive index. Results. Renal resistive index was significantly higher in the SLE with nephritis group compared to the control group. RI was highest in renal class IV, followed by class III, and lowest in class II (0.73±0.08 vs. 0.67±0.07 vs. 0.59±0.06, p < 0.001). The differences were statistically significant between classes II and IV, with no significant differences between class III and either class II or IV. RI showed moderate diagnostic performance in distinguishing SLE patients with nephritis from those without nephritis (AUC = 0.794, 95% CI: 0.672–0.917), sensitivity 76% (CI: 54.9%–90.6%), specificity 68% (CI: 46.5%–85.1%). Conclusion. Renal resistive index is a potentially useful diagnostic tool in lupus nephritis. Larger, prospective, longitudinal studies are needed to confirm these findings.