Background Renal resistive index (RRI) by Doppler ultrasound, reflects changes in both renal vascular and tubular-interstitial compartments and systemic vascular compliance related to physiological (age) and pathological conditions among which hypertension, diabetes mellitus, hyperuricaemia, dyslipidaemia and chronic kidney disease play a major role . Because of the age-related changes in RRI reported in literature [2,3] the use of a 0.70 cut-off to detect renal damage, as proposed , was questioned: renal injury in younger decades (<60yrs) may occur also for RRI value <0.70 and be underestimated. In systemic sclerosis (SSc), RRI was previously correlated with disease duration, glomerular filtration rate and nailfold-videocapillaroscopy pattern [5–7], although tested on small samples and not investigating the possible confounding role of age-related RRI values.
Objectives to describe RRI in a larger scleroderma population and to test both the fixed 0.70 RRI cut-off and age-adjusted cut-offs in reflecting renal and other disease-related organ damage.
Methods SSc patients attending classified according to ACR/EULAR 2013 criteria were enrolled. Data on renal arteries Doppler ultrasound (RRI), autoantibodies status and biochemical tests for renal function/damage, subset and extent of skin fibrosis, instrumental assessment for internal organ involvement were collected and analysed as appropriate with SPSS vers 20.0. Considering that age-adjusted mean values were higher in the SSc population compared to literature values for the general population, we created SSc-specific age-adjusted pathologic cut-offs dividing our SSc population in quartiles and considering RRI values above the 75th percentile as pathologic (Table 1).
Results 190 SSc patients (age 56.3±15.0 years, disease duration 6±8,20 men) were eligible for the study. In the SSc population significant positive correlations between RRI and age, as well as significant associations between RRI and above mentioned general population comorbidities , were confirmed. When considering absolute value of RRI, the 0.70 pathologic cut-off and age-adjusted cut-offs validated in the general population , only renal function, systolic PAP, DLCO and late nailfold scleroderma pattern were associated with RRI (Figure 1). Pathologic RRI identified according to age cut-offs could not detect early renal damage, but was significantly associated with various fibrotic [interstitial lung disease (p=0.015), tendon friction rubs (p=0.032), skin fibrosis vs no skin involvement (p<0.001), higher mRSS (p=0.001)] and vasculopathic manifestations [late scleroderma pattern (p=0.002) and digital ulcers (p=0.006)] of the disease (Figure 1).
Conclusions in clinical practice, different age-related or non-related RRI cut-offs must be used when looking for renal or extrarenal SSc-induced damages.
Boddi, Intern Emerg Med 2015;2)Boddi, Am J Hypertens 1996;3)Ponte, Hypertension 2014;4)Platt, Am J Roentgenol 1989;5)Rivolta,Arthritis Rheum 1996;6)Rosato, Seminar ARthritis Rheum 2012;7)Rosato, Arthritis Care Res 2014.
Disclosure of Interest None declared