Putative intestinal hyperammonaemia in horses: 36 cases.
Authors: Dunkel B, Chaney K P, Dallap-Schaer B L, Pellegrini-Masini A, Mair T S, Boston R
Journal: Equine veterinary journal
Summary
# Intestinal Hyperammonaemia in Horses: Clinical Presentation and Outcomes Hyperammonaemia secondary to intestinal disease remains poorly characterised in equine practice, despite its potential for severe systemic complications. This retrospective analysis of 36 cases (26 adult horses and 10 foals) with confirmed intestinal hyperammonaemia (blood ammonium ≥60 µmol/l, excluding primary hepatic disease) identified a spectrum of gastrointestinal presentations—predominantly colitis and enteritis—accompanied by neurological signs and colic. Clinical and laboratory findings were marked by tachycardia, elevated packed cell volume, hyperlactataemia and hyperglycaemia, reflecting the severity of underlying intestinal inflammation and systemic compromise. Whilst prognosis proved guarded overall, with only 39% surviving to discharge, those that recovered (n=14) showed complete resolution without residual complications, and notably, ammonia concentration at admission was the sole parameter significantly predictive of survival. The findings underscore the need for earlier detection and investigation of intestinal hyperammonaemia's predisposing factors, which remain undefined; practitioners encountering horses presenting with colitis, enteritis or unexplained neurological signs should consider ammonia screening as part of their diagnostic approach, particularly when standard parameters suggest disproportionate systemic derangement.
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Practical Takeaways
- •Intestinal hyperammonaemia should be considered in horses and foals presenting with colic, diarrhoea, or neurological signs; blood ammonium concentration at admission is the most reliable prognostic indicator
- •Affected horses commonly show tachycardia, elevated PCV, and metabolic derangements (hyperlactataemia, hyperglycaemia) that guide supportive care decisions
- •Survivors have excellent long-term prognosis with complete recovery and return to function, justifying aggressive treatment despite severe initial presentation
Key Findings
- •36 cases of intestinal hyperammonaemia identified (26 mature horses, 10 foals) with variable clinical presentations including diarrhoea, colic and neurological signs
- •39% survival rate (14/36 horses) with blood ammonium concentration on admission as the only significant prognostic indicator
- •Common clinical abnormalities included tachycardia, increased packed cell volume, hyperlactataemia and hyperglycaemia
- •All surviving horses and foals with follow-up information recovered completely and returned to intended use without complications