Hemolytic Syndrome in Horses With Liver Failure
Johanna L. Watson • Gary P. Carlson
A fulminant intravascular hemolytic syndrome has been reported as a near-terminal event in horses with either acute or chronic liver failure.1 Marked hemoglobinemia and hemoglobinuria are associated with intense icterus, and the sclera and conjunctiva often take on a distinctive deep reddish-orange color.
The onset of intravascular hemolysis is sudden and rapidly progressive. The prognosis is highly unfavorable; nearly all horses that develop this syndrome do not survive.2The cause of this syndrome is unknown, but release of hepatic copper stores does not appear to be a factor. The hemolysis may be associated with increased erythrocyte osmotic fragility. Human patients with liver cirrhosis develop a hemolytic syndrome associated with alterations in the exchangeable lipoproteins of the red cell membrane. A similar mechanism has not been shown in horses, but morphologic alterations in these horses' red cells resemble the burr cells described in human patients.3 Bile acids and their salts are markedly increased in liver failure and could play a contributing role in the hemolytic process. At necropsy, widespread hemorrhagic lesions that resemble those described for DIC are often present.3