Evaluation of liver stiffness in a population of client owned healthy dogs using two-dimensional shear wave elastography: intraobserver reliability

Sonoelastographic techniques can complement conventional grey-scale and Doppler ultrasonography by evaluating tissue elasticity, which has the prospect to provide differentiation between malignant and benign conditions. Both technical and patient-related confounding factors are known to influence the reliability and reproducibility of elastographic methods. Therefore, the study was designed to assess liver stiffness in a diverse population of client-owned healthy dogs, evaluate the effect of patient characteristics on the elastography measurements and to assess intraobserver reliability. A total of forty dogs underwent two-dimensional shear wave elastography (2D SWE) twice, performed by the same operator, one to six days apart. The average, median and maximum 2D SWE velocities for the linear probe were 2.50 +/- 0.067 m/s; 2.46 +/- 0.067 m/s; 3.58 +/- 0.13 m/s, respectively, and for the convex probe 0.99 +/- 0.11 m/s; 0.98 +/- 0.12 m/s and 1.34 +/- 0.21 m/s, respectively. No statistically significant effect (P> 0.05) on the 2D SWVs was seen of the dog-related characteristics sex, age, body weight and body condition score. The intraobserver agreement of 2D SWE was moderate with the intraclass correlation coefficient (ICC) for the average, median and maximum 2D SWE being 0.69; 0.71 and 0.74, respectively. The moderate ICC and discrepant results obtained with different probes mandates standardization of patient-related and technical factors to overcome excessive variability in measurements in order to implement this technique in clinical practice.