Portal vein anomaly and hepatic encephalopathy in a horse.

The research chronicles the diagnosis and resultant euthanization of a young Thoroughbred horse suffering from hepatic encephalopathy, a brain disease resulting from a liver malfunction, triggered by an unusual formation and blockage in the portal vein.

Background

• The study discusses a case of a yearling Thoroughbred gelding (a young, castrated male horse), suffering from repeated episodes of an abnormal condition affecting the central nervous system (brain and spinal cord).
• The horse had a previous history of frequent respiratory tract diseases and impaired growth.

Diagnosis of Hepatic Encephalopathy

• Hepatic encephalopathy was diagnosed, primarily based on the horse’s medical history and observed clinical signs such as behavioural changes, or neuromuscular abnormalities like weakness or lack of coordination.
• Additional diagnostic tests included prolonged bromsulphalein clearance test which studies the liver’s ability to transport organic anions out of the body and a blood test that revealed increased levels of ammonia. Both tests further pointed toward the likelihood of liver disease or dysfunction.

Euthanization and Post-mortem Findings

• Given the grim prognosis and the relentless recurrence of the clinical symptoms, it was decided to humanely end the horse’s pain and suffering by euthanizing it.
• A post-mortem examination or necropsy was conducted which revealed two key anomalies in the horse’s body: an arteriovenous anomaly – the abnormal direct connection between an artery and a vein – and a thrombosis or blood clot of the portal vein, a large vessel supplying blood to the liver.
• In addition, microscopic examination of the brain tissue showed diffuse primary astrocytosis where there is abnormal increase of astrocytes, star-shaped glial cells in the brain and spinal cord, suggesting a significant brain disorder. The proliferation of astrocytes often occurs in response to injury.