Gastric adenocarcinoma in a horse with portal vein metastasis and thrombosis: a novel cause of hepatic encephalopathy.
Authors: Patton K M, Peek S F, Valentine B A
Journal: Veterinary pathology
Summary
# Editorial Summary: Gastric adenocarcinoma as a cause of hepatic encephalopathy in horses Whilst hepatic encephalopathy in horses typically results from primary liver disease or portosystemic shunting, this 2006 case report documents a rare presentation where gastric adenocarcinoma with hepatic metastasis and portal vein thrombosis was the underlying cause. A 17-year-old Quarter horse mare presented with acute neurological signs—depression, mania, and blindness—over 72 hours, with laboratory findings showing marked hyperammonemia in both plasma and cerebrospinal fluid; necropsy revealed a transmural gastric fundic mass, multiple hepatic masses, and a large neoplastic thrombus occluding the portal vein. Histologically, all lesions comprised similar adenocarcinoma cells with characteristic acinar and cord formations surrounded by dense fibrous stroma, with hepatic pathology including numerous Alzheimer type II astrocytes indicating the brain's response to ammonia accumulation. The clinical significance lies in recognising that portal vein thrombosis—whether primary or secondary to metastatic disease—can severely impair hepatic blood clearance and ammonia detoxification, precipitating encephalopathy without primary hepatocellular dysfunction. For equine practitioners, this case underscores the importance of considering malignancy in differential diagnoses of acute hepatic encephalopathy, particularly when standard liver function parameters may appear relatively preserved despite neurological crisis, and highlights how tumour-related vascular complications can become life-threatening through mechanisms beyond simple hepatic failure.
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Practical Takeaways
- •Gastric neoplasia should be considered in horses presenting with acute neurological signs (depression, mania, blindness) and hyperammonemia, as hepatic encephalopathy can be a presenting sign of advanced malignancy with vascular involvement
- •Portal vein thrombosis secondary to metastatic disease can impair hepatic function and ammonia clearance; assess liver function and ammonia levels in horses with acute encephalopathy
- •This case highlights a rare but serious differential diagnosis for equine hepatic encephalopathy and the importance of thorough post-mortem examination in cases with unusual clinical presentations
Key Findings
- •Gastric adenocarcinoma with portal vein metastasis and thrombosis caused hepatic encephalopathy in a 17-year-old Quarter horse mare
- •Hyperammonemia and portal vein thrombosis were identified as key pathogenic mechanisms in this case of hepatic encephalopathy
- •Clinical presentation included depression, mania, blindness, and mild icterus over 72 hours preceding death
- •Histopathology revealed Alzheimer type II astrocytes throughout the cerebral frontal cortex, consistent with hepatic encephalopathy