Background: Since liver fibrosis is one of the most accurate predictors of prognosis in hepatopatic patients, its accurate assessment and staging is a major public health issue. Transient elastography (TE) (Fibroscan, Echosens, Paris, France) and shear wave elastography (SWE) represent the gold standard techniques among non-invasive methods to assess liver fibrosis. Contrast-enhanced ultrasound (CEUS) is increasingly used to diagnose the nature of liver lesions and is often performed together with TE and SWE. In this study we evaluated the effect of CEUS on liver stiffness measurements obtained by TE and SWE.
Methods: A retrospective analysis of ultrasound (US) exams performed by an expert operator was carried out. TE and SWE were performed 30 seconds before and after the execution of CEUS. Statistical analysis was carried out using the statistical software R. Kolmogorov-Smirnov analysis was performed to test the normality of continuous variables. The pre- and post-CEUS liver stiffness values were compared using the Wilcoxon's Test.
Results: Ninety-six patients were enrolled. While the measurements were comparable when performed with TE, those obtained by SWE decreased by 6% after administration of the contrast agent (P=0.0005). Fibrosis stage deviated between pre- and post-CEUS in 16 (17%) patients with Fibroscan and 22 (23%) patients with SWE. Among the latter, in 9 cases (10%) a deviation from absent-low (F0-F2) to high-fibrosis (F3, F4), or vice versa, occurred.
Conclusions: Our study, the first to assess the effects of CEUS on US elastography, shows that the contrast agent (Sonovue, Bracco Suisse SA, Cadempino, Switzerland) does not significantly affect liver stiffness measurements obtained by TE, whereas the accuracy decreases when performed by SWE.