Washout Ratio in the Hepatic Vein Measured by Contrast‐Enhanced Ultrasonography to Distinguish Between Inflammatory and Noninflammatory Hepatic Disorders in Dogs

BACKGROUND Perflubutane microbubbles, a second-generation ultrasound contrast agent, are phagocytized by Kupffer cells. This characteristic may be useful to differentiate diffuse hepatic diseases in dogs. HYPOTHESIS/OBJECTIVES To determine whether the washout ratio in the hepatic vein (HV) measured by contrast-enhanced ultrasonography (CEUS) can distinguish between inflammatory and noninflammatory hepatic disorders in dogs. ANIMALS Forty-one client-owned dogs with hepatic disorders including 14 with hepatitis, 7 with primary hypoplasia of the portal vein (PHPV), 9 with congenital portosystemic shunt (cPSS), and 11 with other hepatopathy were enrolled. Six dogs without hepatic disease also were evaluated as healthy controls. METHODS Dogs with hepatic disorders were prospectively included. Contrast-enhanced ultrasonography of the HV was performed for 2 minutes. Washout ratio was defined as the attenuation rate from peak intensity to the intensity at the end of the CEUS study. RESULTS Washout ratio in the hepatitis group (median, 18.0%; range, 2.0-37.0%) was significantly lower than that of the PHPV (median, 52.2%; range, 11.5-86.3%), cPSS (median, 60.0%; range, 28.6-77.4%), other hepatopathy (median, 70.5%; range, 26.6-88.4%), and normal (median, 78.0%; range, 60.7-91.7%) groups. The area under the receiver operating characteristic curve for hepatitis was 0.960, with a 95% confidence interval (CI) of 0.853-0.990. Washout ratio ≤37.1% resulted in a sensitivity of 100% (95% CI, 78.5-100%) and specificity of 85.2% (95% CI, 67.5-94.1%) for the prediction of hepatitis. CONCLUSIONS AND CLINICAL IMPORTANCE Washout ratio can distinguish hepatitis from the other noninflammatory disorders with high accuracy. This result might reflect impaired Kupffer cell phagocytosis in dogs with hepatitis.