Ultrasonographic evaluation of renal resistive index in patients with lupus nephritis: correlation with histologic findings

Renal arterial resistive index as a prognostic marker in lupus nephritis patients

INTRODUCTION

Lupus nephritis (LN) is known to be one of the most serious complications of SLE and it is a major predictor of poor prognosis. Despite the improvement in understanding the pathophysiology of lupus nephritis and greater improvement in diagnostic approaches, lupus nephritis patients have poorer outcomes.

OBJECTIVES

Study the relation between renal resistive index (RRI) and renal function and histopathological parameters in lupus nephritis (LN) patients. Also to investigate the usefulness of RRI in predicting response to treatment.

PATIENTS AND METHODS

This study included 126 patients who were split into two groups (group 1: 101 LN patients and group 2: 25 SLE patients without renal affection); and 100 healthy controls (group 3). The RRI was measured for all participants through a colored Doppler ultrasound examination. LN patients underwent renal biopsy and received their therapy and were followed up for 6 months.

RESULTS

The RRI was significantly greater in the LN group (mean±SD; 0.64±0.07) than in SLE patients without nephritis (0.5884±0.04) (P<0.0001). The RRI was greater in LN class IV (P<0.0001). RRI significantly correlated with the chronicity index (r=0.704, P<0.0001), activity index (r=0.310, P=0.002), and serum creatinine (r=0.607, P<0.0001) and negatively correlated with eGFR (r=-0.719, P<0.0001). Almost eighty-five percent (84.8%) of LN patients responded to induction therapy. RRI was significantly greater in the nonresponder group (mean±SD, 0.73±0.02) than that in the responder group (0.63±.07) (P<0.0001). All non-responders to induction therapy while only 29.8% of responders had an RRI of ˃0.7. RRI, according to regression analysis was a significant predictor of response to treatment in LN patients.

CONCLUSION

RRI was significantly greater in the LN group and significantly correlated with kidney function and histopathological parameters. RRI can predict response to induction therapy in LN patients.

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.

Renal resistive index in IgA nephropathy and renal scleroderma vasculopathy

BACKGROUND

Renal Ultra-Sound (US) and Doppler US provide measurements which reflect changes in renal and systemic haemodynamic. The renal resistive index (RRI), obtained through the Doppler spectrum analysis of renal small arteries, is altered in several pathologic conditions. Glomerulonephritis cause minor RRI changes, while renal scleroderma vasculopathy (RSV) leads to significant RRI modifications. The aim of our study was to assess RRI in IgA nephropathy (IgAN) and RSV in a retrospective observational study and to investigate determinants of the RRI in these groups of patients.

METHODS

We enrolled 61 IgAN patients [23 female, median age 41 (33-58) years] and 80 SSc patients [71 female, median age 52 (43-60) years]. RRI was evaluated in all patients at the time of enrolment. Laboratory tests and clinical assessment were evaluated in all patients.

RESULTS

IgAN patients showed lower RRI values than RSV patients [0.70 (0.65-0.73) vs 0.66 (0.62-0.72), p < 0.01], while no significant difference in longitudinal length was observed. Median age was significantly lower in IgAN patients than in RSV patients [41 (33-58) vs 52 (43-60), p < 0.05] while IgAN patients showed a higher prevalence of high blood pressure than RSV patients (39.3% vs 13.8%, p < 0.01). The multiple regression analysis, weighted for age, showed that RRI inversely correlates with estimated glomerular filtration rate (β coefficient = -0.524, p < 0.0001).

CONCLUSION

Higher RRI were found in RSV patients than IgAN patients. IgAN is characterized mainly by glomerular injury, not leading to major RRI changes.

Association of Renal Resistive Index with Markers of Extrarenal Vascular Changes in Patients with Systemic Lupus Erythematosus

Recent data suggest that renal hemodynamic parameters obtained by duplex Doppler sonography, especially the intrarenal resistive index (RRI), may be associated with systemic vascular changes. We evaluated the relationships between RRI and arterial stiffness, assessed by aortic pulse wave velocity, and between RRI and subclinical atherosclerosis, assessed by measuring carotid intima-media thickness in patients with systemic lupus erythematosus. We enrolled 39 patients with systemic lupus erythematosus (mean age 39 y) compared with 19 healthy controls, matched for age and sex. Each participant underwent 24 h of ambulatory blood pressure, aortic pulse wave velocity, carotid intima-media thickness and RRI measurements. RRI correlated significantly with aortic pulse wave velocity (r = 0.44, p = 0.006), and with carotid intima-media thickness (r = 0.46, p = 0.003). Both correlations held (p = 0.01), even after correction for age, mean arterial pressure and glomerular filtration rate. Our results suggest that the RRI may be considered a marker of systemic vascular changes and probably a predictor of cardiovascular risk in patients with systemic lupus erythematosus.

Renal parenchymal resistance in patients with biopsy proven glomerulonephritis: Correlation with histological findings

Renal Doppler ultrasound is increasingly used in nephrology for the evaluation of renovascular disease, allograft dysfunction, and chronic nephropathies. We compared intrarenal hemodynamic parameters to biopsy findings of glomerular sclerosis, tubular atrophy, interstitial fibrosis, crescents, arteriolosclerosis, and clinical variables in 100 patients. A positive correlation exists between renal function and percentage of glomerular sclerosis (P <0.01, r = 0.26), conversely a negative correlation exists between glomerular filtrate rate and percentage of glomerular sclerosis(P <0.0001, r = -0.35). The percentage of glomerular sclerosis correlate positively with pulsatile index (PI) (P <0.05, r = 0.21) and renal resistive index (RI) (P <0.05, r = 0.20). The percentage of crescents correlates positively with PI(P <0.05, r = 0.21) and RI (P <0.05, r = 0.20). Classifying arteriolosclerosis in four groups according to a severity scale, from absence to severe, PI (P <0.05) and RI (P <0.01) were significantly different. In the post hoc analysis, the median values of PI and RI are significantly different in patients with severe arteriolosclerosis than others. Ultrasound examination is a non-invasive diagnostic technique used on patients with suspected or established renal disease. Our study shows a close correlation between kidney function, ultrasound parameters, and histological findings. Measurement of renal parenchymal resistance by ultrasound could be used in association with biopsy and glomerular function for the evaluation of renal damage in patients with glomerulonephritis.

Genetic Factors in Systemic Lupus Erythematosus: Contribution to Disease Phenotype

Genetic factors exert an important role in determining Systemic Lupus Erythematosus (SLE) susceptibility, interplaying with environmental factors. Several genetic studies in various SLE populations have identified numerous susceptibility loci. From a clinical point of view, SLE is characterized by a great heterogeneity in terms of clinical and laboratory manifestations. As widely demonstrated, specific laboratory features are associated with clinical disease subset, with different severity degree. Similarly, in the last years, an association between specific phenotypes and genetic variants has been identified, allowing the possibility to elucidate different mechanisms and pathways accountable for disease manifestations. However, except for Lupus Nephritis (LN), no studies have been designed to identify the genetic variants associated with the development of different phenotypes. In this review, we will report data currently known about this specific association.

Ultrasonographic Evaluation of Resistive Index and Renal Artery Stenosis in Patients with Anti-Phospholipid Syndrome: Two Distinct Mechanisms?

Renal involvement in anti-phospholipid syndrome (APS) is still relatively unknown and probably underestimated. The described lesions consist of renal artery stenosis (RAS), venous renal thrombosis and glomerular lesions. The resistive index (RI) of intra-renal arteries, expression of the degree of vascular resistance, has been analyzed in different nephropathies and observed to be associated with functional parameters and some histologic features. In contrast, there are no studies on patients with APS. We evaluated the presence of a pathologic RI and RAS in a cohort of patients with APS. The study protocol included ultrasonographic assessment to measure the RI (RIs >0.7 were considered pathologic) and to determine the presence of RAS. We enrolled 36 patients with APS, 13 with primary APS and 23 with the form associated with systemic lupus erythematosus (SLE, secondary APS). As controls, we enrolled 10 anti-phospholipid antibody carriers, 10 patients with SLE without renal involvement and 14 age- and sex-matched healthy patients. A pathologic RI was identified in five patients with APS (13.9%) and in none of the anti-phospholipid antibody carriers (p = 0.00007). Four of the five (80%) patients with a pathologic RI had secondary APS. Three patients, all with primary APS, had RAS. The almost exclusive association of a pathologic RI with secondary APS and of RAS with primary APS suggests the involvement of two pathogenic pathways in the development of these different manifestations. The hypercoagulability status driven by APS could play a central role in the determination of RAS in patients with primary APS, whereas the activation of mTORC (mammalian target of rapamycin complex) pathways could be the pathogenic mechanism inducing development of a pathologic RI.