Factors other than fibrosis that increase measured shear wave velocity

Abstract

Shear wave elastography (SWE) is now becoming an indispensable diagnostic tool in the routine examination of liver diseases. In particular, accuracy is required for shear wave propagation velocity measurement, which is directly related to diagnostic accuracy. It is generally accepted that the liver shear wave propagation velocity reflects the degree of fibrosis, but there are still few reports on other factors that increase the shear wave propagation velocity. In this study, we reviewed such factors in the literature and examined their mechanisms. Current SWE measures propagation velocity based on the assumption that the medium has a homogeneous structure, uniform density, and is purely elastic. Otherwise, the measurement is subject to error. The other (confounding) factors that we routinely experience are primarily: (1) Conditions that appear to increase the viscous component; and (2) Conditions that appear to increase tissue density. Clinically, the former includes acute hepatitis, congested liver, biliary obstruction, etc, and the latter includes diffuse infiltration of malignant cells, various storage diseases, tissue necrosis, etc. In any case, it is important to evaluate SWE in the context of the entire clinical picture.

Keywords: Liver, Shear wave elastography, Propagation velocity, Viscoelasticity, Artifact, Ultrasound

Core Tip: Shear wave elastography (SWE) has become an indispensable diagnostic tool for diagnosing liver disease patients. The shear wave propagation velocity usually reflects the degree of fibrosis, but we must keep in mind other (confounding) factors. The confounding factors due to viscosity include acute hepatitis, congestive liver, and biliary stasis. The other confounding factors due to an increase of tissue density include diffuse infiltration of malignant cells, various storage diseases, and tissue necrosis. It is important to judge SWE results in the context of the entire clinical picture.