Prognostic Role of Measurement of Renal Resistive Index in Systemic Sclerosis.

Objective: The spectrum of vascular involvement in systemic sclerosis (SSc) includes digital ulcers, gangrene, Raynaud's phenomenon, renovascular disease, and pulmonary hypertension (PH). Recognition of markers of subclinical vascular disease in SSc is an area of active research, but such studies are limited. This study assesses the role of measurement of the renal resistive index (RRI) as an early marker of renal and systemic vasculopathy. It is a step forward towards examining the possibility of a "unified vascular phenotype' in SSc.

Methods: In this single-centre prospective study, RRI was calculated for SSc patients >18 years age. Elevated RRI (>0.7) was correlated with renal function (eGFR and proteinuria) and systemic vasculopathy manifestations like digital ulcers, digital infarcts, and PH.

Results: A total of 73 patients with mean (SD) age 41.8(10.9) years were included. Mean (SD) RRI in the right and left renal artery was 0.65(0.08) and 0.66(0.07), respectively. 16 (21.9%) patients had elevated RRI (>0.7). A strong negative correlation was noted between elevated RRI and eGFR (r= -0.96, p=0.03). The percentage of patients with overt proteinuria was higher in the group with elevated RRI (20% versus 7%) (p=0.16). Similarly, digital ulcers (56% vs 33%) and digital pitting (50% vs 35%.) were numerically higher in the group with raised RRI, although statistical significance was not reached because of small numbers (p=0.09 and 0.28, respectively). No correlation of RRI with PH was identified.

Conclusion: RRI correlates well with asymptomatic renal dysfunction and holds promise in the assessment of systemic vasculopathy. However, validation in studies with a larger sample size is needed.