Two-dimensional shear wave elastography of liver in healthy dogs: anaesthesia as a source of variability

Two-dimensional shear wave elastography (2D-SWE) is a non-invasive method to quantitatively evaluate the liver stiffness (LS), allowing the detection of hepatic pathological changes in both dogs and humans. In dogs, some factors such as patient movement and respiration can cause artefacts and potential errors of measurements. Therefore, anaesthesia has been suggested to reduce the effect of the movement on 2D-SWE in dogs. This study was performed to evaluate the influence of an anaesthetic protocol on 2D-SWE measurements for assessment of LS in healthy dogs. Forty-five dogs were included and subjected to anaesthesia: in 11 dogs, the 2D-SWE was performed both before and under anaesthesia, in 19 dogs, the 2D-SWE was performed only when they were awake and in 15 dogs, the examination was carried out only under anaesthesia. The anaesthetic protocol was composed of intramuscular injection of a combination of dexmedetomidine, methadone and ketamine and intravenous administration of propofol for induction and isoflurane for maintenance. The variability of 2D-SWE values according to anaesthesia was evaluated. Median 2D-SWE values were significantly higher in anesthetized dogs compared to awake dogs either by considering separately the dogs in which the examination was performed both awake and under anaesthesia and by considering all dogs included. According to our study, anaesthesia helped to avoid challenges related to patient movement and respiration; however, it was a source of variability on 2D-SWE values, and this factor should be considered before performing 2D-SWE under anaesthesia.