SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
Liver disease in horses is often a subclinical problem and in some instances , there may just be vague complaints of poor performance , dullness or ill thrift in affected horses . Elevations of one or more liver enzymes should prompt sonographic evaluation of the liver . There are a variety of insult to the liver that cause hepatopathy in the horse including toxic , infectious , inflammatory , and fibrotic , among others . Sonographic examination of the liver can be helpful in differentiating these but a liver biopsy with culture and sensitivity testing is necessary for a definitive diagnosis . The role of the newly discovered equine liver viruses remains to be determined .
In horses with cholangiohepatitis or biliary obstruction , the liver is usually larger than normal livers with increased parenchymal echogenicity . Biliary distension , sludging of bile within the ducts , thickening of the bile ducts and hepatoliths may be imaged in the biliary tree . The parallel channel sign ( a dilated tubular structure running parallel to the portal blood vessels ) is useful in identifying biliary distention .
Parallel channel sign with cholangiohepatitis
Color flow Doppler and power Doppler can be used to differentiate dilated bile ducts from portal blood vessels . The obstructing hepatoliths are most commonly found cranioventrally , in the 6th through 9th intercostal spaces , while biliary distension is usually imaged caudodorsally . Hepatoliths are usually hyperechoic and cast acoustic shadows .
Increased echogenicity of the hepatic parenchyma occurs with granulomatous , inflammatory , fibrotic , neoplastic or fatty infiltration of the liver . Hepatic lymphosarcoma may have a uniform homogeneous appearance with diffuse infiltration of the liver or may be imaged as homogeneous or complex , composite masses within the hepatic parenchyma . A significantly poorer prognosis has been reported for horses with liver disease when ultrasonographic abnormalities are present . An association between hepatic fibrosis , hemosiderosis and moderate or severe biliary hyperplasia has also been reported in horses with ultrasonographically detected hepatic abnormalities .
Vascular ultrasonography
Thrombophlebitis Venous thrombosis and thrombophlebitis are common problems in performance horses and can be associated with poor performance . Complete occlusion of the jugular vein can lead to venous congestion in the head and proximal cervical region which can worsen with exercise , resulting in unilateral swelling of the head and pharyngeal structures due to impaired venous drainage of the upper airway .
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