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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. 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). 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. 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. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the accuracy of quantitative ultrasonic measurements of renal allograft elasticity and viscosity using shear wave elastography (SWE) Aixplorer Mach 30 ultrasound system (Supersonic Imagine, Aix-en-Provence, France). 2D-SWE was performed on 35 kidney transplanted patients (13 women, 22 men) with a mean age of 48.45±13.33 years and mean estimated glomerular filtration rate(eGFR) 52.19±22.28ml/min/1.73m2. One nephrologist took 5 quantitative measures of renal cortical elasticity and viscosity, in 5 different frames, which were represented in terms of Young's modulus (kPa) respectively Viscosity Plane-wave Ultra-Sound (Vi-Plus) in Pa.s. The intraclass correlation coefficient, as well as intraobserver reproducibility (Bland-Altman plot with multiple measures per subject), were evaluated. We obtained 5 valid measurements in every studied patient, with a mean measurement stability index (SI) tool accuracy of 92.5%±1.95%. We found no correlation between median depth of measurements and median SI, or between kidney length (cm) and median SI, but we found a positive correlation between body mass index (BMI) and mean depth of measurements (r=0.7029, P<0.0001, 95% CI for r 0.4739 to 0.8428). Our study shows a good intraclass correlation coefficient for mean values of transplanted renal cortical elasticity with average measures of 0.9551, 95% CI 0.926 to 0.974 as well as for Vi-Plus with average measures of 0.8338, 95% CI 0.728 to 0.907. The Bland-Altman plot with multiple measures per subject displays a mean of 23.2±1.96 with a lower limit of 8.5 and an upper limit of 37.8. 2D-SWE with Aixplorer Mach 30 system shows a good intraclass correlation coefficient as well as good intraobserver reproducibility for both measures in renal cortical elasticity and viscosity. This can prove to be a low-cost way to provide additional diagnostic information in kidney transplanted patients. Further studies are required for this method to be introduced routinely into clinical practice. [ABSTRACT FROM AUTHOR]

Elastography comes as a useful noninvasive tool for the assessment of renal transplant recipients, but there is however a great heterogeneity between the studies performed with different elastographic methods. 2D-shear wave elastography (SWE) PLUS emerges as a novel technique that promises to offer improved renal stiffness measurements due to improved processing algorithms. We performed a cross-sectional study of 35 kidney transplanted patients (13 women, 22 men, with a mean age of 49.4±13 and a mean duration after transplant 10.1±5 years). In every patient, we obtained 5 valid measurements of renal stiffness (obtained from 5 different frames in the cortex of the renal graft), and also tissue viscosity (Viscosity Plane-wave Ultrasound-VI-Plus), with a C6-1X convex transducer using the Ultra-Fast™ software available on the Aixplorer Mach 30 ultrasound system (Supersonic Imagine, Aix-en-Provence, France). The median value of elastographic measurements has been correlated with the demographic and clinical parameters of the patients. We obtained a cut-off value of renal cortical stiffness of <27.3kPa for detection of estimated glomerular filtration rate(eGFR)<60ml/min/1.73m2 with 80% sensitivity and 75% specificity (AUC=0.777, P=0.0001), a cut-off value of <26.9kPa for detection of eGFR<45ml/min/1.73m2 with 70.33% sensitivity and 70% specificity (AUC=0.718, P=0.014) and a cut-off value of <23kPa for detection of eGFR<30ml/min/1.73m2 with 85.7% sensitivity and 75% specificity (AUC=0.837, P<0.001). We found a positive correlation coefficient of renal cortical stiffness and the eGFR (r=0.4855, P=0.0031, 95% CI for r 0.1817 to 0.7048), also with viscosity (r=0.4640, P=0050, 95% CI for r 0.1546 to 0.6905), and a negative correlation with measurement depth (r=-0.3388, P=0.0465, 95% CI for r -0.6038 to -0.0061). No statistically significant correlations were found between mean measures of cortical stiffness and age, hypertension, diabetes, previous glomerular disease, or if the kidney was attained from a living related or a deceased donor or between C reactive protein and viscosity. Renal stiffness in transplanted patients shows a major statistical correlation with renal function, thus kidneys with reduced renal function show significantly decreased stiffness values. More research is needed to validate this technique for it to be used in regular clinical practice. [ABSTRACT FROM AUTHOR]