Peer-reviewed veterinary case report
Postmortem diagnosis of idiopathic hyperammonemia in a horse.
- Journal:
- Veterinary clinical pathology
- Year:
- 2007
- Authors:
- Gilliam, Lyndi L et al.
- Affiliation:
- Department of Veterinary Clinical Sciences · United States
- Species:
- horse
Plain-English summary
A 6-year-old Quarter Horse stallion was taken to a veterinary hospital because he was experiencing abdominal pain after breeding. Within a day, he developed diarrhea and serious neurological issues, like circling and confusion, and was ultimately euthanized due to severe self-harm. Tests showed low calcium levels but no signs of liver disease, leading to a suspicion of idiopathic hyperammonemia (high ammonia levels in the blood) and related brain issues. After his death, tests revealed very high ammonia levels in his blood and other fluids compared to healthy horses, suggesting that checking ammonia levels postmortem can help diagnose this condition in horses. Unfortunately, the treatment options were not effective in saving the stallion.
Abstract
A 6-year-old Quarter Horse stallion was referred to Oklahoma State University Veterinary Medical Teaching Hospital for evaluation of abdominal pain that developed after breeding activity earlier in the day. The horse developed diarrhea and progressively worsening neurologic signs (circling, ataxia, head pressing) within 22 hours of presentation and was subsequently euthanized due to severe self-destructive behavior. Antemortem biochemical and hematologic abnormalities included hypocalcemia but no evidence of hepatic disease. Idiopathic hyperammonemia and encephalopathy were suspected; cerebrospinal fluid (CSF) and aqueous humor were collected 10 hours postmortem for ammonia analysis using a colorimetric assay. Results were compared with those of 6 horses that also had been euthanized, for diseases unrelated to encephalopathy. Ammonia also was measured in plasma samples obtained antemortem. Ammonia concentrations in plasma (958 micromol/L), CSF (1566 micromol/L) and aqueous humor (1018 micromol/L) samples from the stallion were markedly increased compared to those in the 6 unaffected horses (plasma, 9-43 micromol/L; CSF, 370-532 micromol/L; aqueous humor, 70-483 micromol/L). Since the acute nature of hyperammonemic encephalopathy often does not provide sufficient time for an antemortem diagnosis, postmortem analysis of CSF and aqueous humor ammonia concentrations may be a useful alternative for documenting hyperammonemia in horses.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/17523096/