Measurement of Renal Artery Resistive Index as a Predictor of Severity of Lupus Nephritis and Its Response to Treatment

LN is known to be one of the most serious complications of SLE and it is the major predictor of poor prognosis. In the United States, approximately 35% of adults with SLE have clinical evidence of nephritis at the time of diagnosis; with an estimated total of 50 to 60% developing nephritis during the first 10 years of disease. Lupus nephritis is diagnosed by either the presence of proteinuria (>0.5 g/day), active urinary sediment (with red blood cell, granular, tubular and/or mixed casts), or an unexplained rise in serum creatinine (S Cr). A kidney biopsy is the gold standard to diagnose LN as it provides information regarding the pattern and severity of renal involvement as well as the stage, activity and chronicity. These are all important considerations influencing treatment decisions. However, the invasive nature make it contraindicated in certain situation like bleeding tendency. In one report, five of seven patients with significant bleeding after renal biopsy were patients with LN. Serial biopsy may be needed to monitor progression and treatment. This will increase risk of complication and may be not practical.

The renal arterial resistive index (RRI) is a sonographic index to assess for renal arterial disease. It is measured as:

RRI = (peak systolic velocity - end diastolic velocity) / peak systolic velocity .The RRI was introduced in 1950, and was initially proposed for the semi-quantitative assay of intra-renal vascular resistance by Gosling and Pourcelot in 1974. RRI is and markedly affected by renal determinants such as renal interstitial and venous pressure. In humans in vivo, the acute increase of renal interstitial pressure by hydronephrosis or of venous pressure by venous thrombosis, or of both by abdominal hypertension, results in a linearly related increase in RRI. Increases in the RRI have been observed in a number of pathological conditions, which increase renal interstitial and venous pressure such as renal allograft acute rejection, parenchymal nephropathies, acute kidney injury, renal artery stenosis, chronic kidney disease (CKD), diabetic nephropathy, obstructive nephropathy. Remarkably, interstitial fibrosis closely correlates to renal function and long term prognosis, and may underlie the role of RRI as an independent marker of renal and clinical outcome in chronic renal diseases. No standard, validated, cut-off to distinguish normal from high RRI has been identified to date. RRI values between 0.7 and 0.85 have been associated with renal functional impairment in patients with chronic kidney disease and stenosis of the renal artery. Previous data have revealed a significant correlation between the increased RRI value (RRI>0.7) and renal functional parameters (creatinine and blood urea nitrogen levels) and/or histological finding, such as glomerulosclerosis, tubulointerstitial damage and vascular lesions. Few studies evaluate the role of RRI as marker of severity in LN and its potential use as non-invasive marker in the assessment of the outcomes and in treatments response. To date, the usefulness of RRI in monitoring the progression and treatment of LN is controversial.

Type of the study: : observational analytic cross sectional study - cohort study (the part of the study in which the patients of LN are followed for six month receiving the usual treatment according to KDIGO( Kidney Disease: Improving Global Outcomes) guidelines 2012 to demonstrate the response to treatment in patient with pathological RRI compared to with normal RRI) - Study Setting: Assiut University Hospital (internal medicine departments)

All patients with SLE that will be admitted in internal medicine department from August 2019 to January 2021 are eligible to be targeted and included in the study. The diagnosis of SLE will be according to the 1997 American college of Romatology revised criteria (Hochberg 1997). SLE patients with lupus nephritis will take kidney biopsy for standard care of management according to American college of Romatology guidelines 2012. The study will include three groups as follow: