BackgroundFibromuscular dysplasia (FD) is a non-atherosclerotic, non-inflammatory arterial disease of unknown cause, and most frequently affects the renal and internal carotid arteries. Our objectives were to determine whether quantitative and qualitative lesions could be detected by high-resolution echotracking techniques at two arterial sites generally considered as free of echographic lesions: the common carotid and the radial arteries, and to compare their frequency with a control population.Methods and resultsWe studied 70 patients with renal FD and 70 control subjects matched for age, sex and systolic blood pressure. Arterial parameters were determined using non-invasive high-resolution echotracking systems. Carotid B-mode scans and radiofrequency signals were analysed and quoted by three observers blinded to diagnosis. FD patients had thicker carotid (+12%,P<0.001) and radial arteries (+10%,P<0.05) than controls. Abnormal echographic patterns of the carotid artery, including supernumerary interfaces and/or interruption of the blood–intima acoustic interfaces, were frequently observed in FD patients and rarely in control subjects. These abnormalities were quantified with a phenotypic score ranging from 2 to 7, and their sensitivity and specificity were 73 and 81%, respectively, as markers of FD. Having a phenotypic score>3 conferred an odds ratio of 12.9 (95% CI 5.7–29.3) of having renal FD.ConclusionWe defined a new carotid phenotype in FD patients using a non-invasive echotracking system, and showed an increased wall thickness and distensibility of the radial artery. These data indicate the presence of subclinical lesions at arterial sites distant from the renal arteries, suggesting that renal FD is not a focal but a systemic arterial disease.