The Renal Resistive Index in systemic sclerosis: Determinants, prognostic implication and proposal for specific age-adjusted cut-offs

Renal Resistive Index (RRI), reflects changes in both renal vascular and tubular-interstitial compartments and in systemic vascular compliance related to age and comorbidities. a) To investigate determinants of RRI in SSc population, b) its association with SSc-related features and c) to test its prognostic impact on organ specific worsening or death. 380 SSc patients ≥18 years were enrolled after giving informed consent. Baseline data on RRI, laboratory, instrumental and therapeutic features were retrospectively collected. Age-SSc adjusted cut-offs were created by dividing the population in age quartiles and considering RRI values >75th percentile as pathologic. Clinical follow-up was performed until last available visit or the development/worsening of specific internal organ involvement or death. RRI was independently predicted by age and systolic pulmonary arterial pressure on Echo. Therefore, we created Age-SSc adjusted pathologic RRI cut-offs, which were significantly associated with various disease related skin and lung fibrotic manifestations, as well as vasculopathic complications. After a mean follow-up of 3.6 ± 2.6 years, RRI was one of the independent predictors (together with modified Rodnan skin score, interstitial lung disease, presence of dyspnoea and late nailfold-videocapillaroscopy pattern) for mortality, with 0.68 as best cut-off (sensitivity 88.5%, specificity 50.9%). If corroborated, Renal Resistive Index cut-offs might be used to evaluate renal and extrarenal involvement in SSc and could serve as predictors of mortality. •Renal Resistive Index (RRI) is applicable in systemic sclerosis.•RRI reflex renal and extra-renal involvement in scleroderma.•RRI has prognostic impact on mortality.•Age-SSc adjusted cut offs should be used when measuring RRI in scleroderma patients.