Utility of renal resistive index measurement in juvenile systemic lupus erythematosus: a cross-sectional single-center study

Introduction Systemic lupus erythematosus (SLE) is a multisystemic autoimmune disease with a complex etiopathogenesis. Renal involvement is the most common and devastating complication of the disease. Renal resistive index (RRI) was suggested as a noninvasive biomarker for lupus nephritis in previous studies. This is the first study to investigate the role of RRI measurement in juvenile SLE patients. Methods This cross-sectional study included 25 juvenile SLE patients and 25 healthy controls. Demographic and clinical features were recruited from the medical files of the patients. RRI measurements were performed with color Doppler ultrasonography from intrarenal arteries when Doppler angles were 30–60 in right and left kidneys. Results Of 25 (19 female, 6 male) SLE patients, nineteen (76%) patients had urinary abnormalities during follow-up, and renal biopsy was performed in 14 patients, of which 9 (64.3%) had class 2 and 5 (35.7%) had class 4 lupus nephritis. RRI was found significantly higher in SLE group than healthy controls. RRI did not differ between SLE patients, grouped according to the presence of renal involvement and class IV lupus nephritis. RRI did not correlate with serum creatinine, GFR, spot urine protein/creatinine, and albumin/creatinine ratio. Conclusions Although RRI was found significantly higher in juvenile SLE, it is not affected by GFR, proteinuria level, or the renal biopsy results, even the presence of proliferative nephritis. The underlying pathogenetic mechanisms of increased RRI in SLE should be clarified in further studies. Key Points • Renal resistive index (RRI) is a parameter derived from renal Doppler ultrasound imaging and shows the intrarenal arterial resistance. • This study reveals that RRI is increased in juvenile systemic lupus erythematosus. • RRI was previously related with renal involvement, particularly class 4 lupus nephritis in adults. However, RRI was not affected by the presence or degree of renal involvement in juvenile SLE patients in our study.