Clinical evaluation of viscoelasticity measurements by shear wave elastography in healthy and chronic liver disease subjects

Objectives Liver fibrosis is the most significant prognostic factor in chronic liver disease (CLD). Clinical practice guidelines recommend the use of non-invasive techniques, such as two-dimensional shear-wave elastography (2D-SWE), to assess liver elasticity as a marker of fibrosis. It is presumed that changes due to necro-inflammation modify the propagation of shear waves [1]. Therefore, new imaging techniques that investigate the dispersion properties of shear waves have been developed, which can serve as an indirect method of measuring liver viscosity (Vi PLUS). This study aims to analyze the performance of SWE to assess viscosity, to analyze factors influencing Vi PLUS measurements in a large cohort of patients with CLD, and to assess the normal ranges of liver viscosity measurements in participants with healthy livers. Materials 867 consecutive adult subjects were enrolled in this prospective study (199 with healthy livers and 668 with CLD). Subjects were first examined using the Supersonic MACH® 30 US system (Hologic® SuperSonic® Imagine, Aix-en-Provence, France). Gray-scale US, as well as 2D-SWE and Vi PLUS measurements were performed. Secondly, TE measurements were performed with a FibroScan® Compact 530 device (EchoSens®, Paris, France). Results The mean Vi PLUS values in normal, ALD, HBV, HCV, NAFLD patients were: 1.6±0.3 Pa·s, 2.8±0.8 Pa·s, 1.9±0.3 Pa·s, 2.1±0.5 Pa·s and 2±0.4 Pa·s respectively (table 1). The mean Vi PLUS values were significantly higher in subjects with chronic liver disease than in normal subjects, independent of the etiology (p>0.05). Mean Vi PLUS values were significantly higher in subjects with ALD compared to HCV (p<0.0001), HBV (p<0.0001) and NAFLD subjects (p<0.0001); significantly higher in subjects with HCV compared to HBV (p=0.0001) and NAFLD subjects (p=0.011). No significant differences were found between HBV and NAFLD subjects (p=0.0615).In univariate regression analysis, Vi PLUS measurements were independently associated with: BMI (p<0.001), abdominal circumference (p<0.001), age (p<0.001), AST (p<0.001), ALT (p=0.009), the presence of diabetes mellitus (p<0.0001) and the presence of arterial hypertension (p<0.001). In multiple regression analysis the model including: abdominal circumference (p<0.0001), AST (p<0.0001) and ALT values (p=0.0029) was associated with ViPLUS measurements. Conclusions Vi PLUS and 2D-SWE by SSI are highly feasible methods. The mean liver viscosity determined by Vi PLUS in our cohort of participants with healthy livers was 1.69 Pa·s. CLD patients had significantly higher viscosity values. Increased liver stiffness, high transaminases and obesity were associated with high viscosity values.