Putative intestinal hyperammonaemia in horses: 36 cases

P>Reasons for performing the study: Intestinal hyperammonaemia (HA) has been infrequently reported in individual horses; however, there have been no studies describing clinical and laboratory data as well as short- and long-term outcome in a larger number of cases. Objectives: To describe clinical and laboratory data and short- and long-term outcome in a large group of horses with intestinal HA. Methods: Multi-centred, retrospective study; case records of horses with HA were reviewed and any horse with a clinical or post mortem diagnosis of intestinal HA was included. Hyperammonaemia was defined as a blood ammonium (NH4+) concentration >= 60 mu mol/l and horses with a diagnosis of primary hepatic disease were excluded. Relevant data were recorded and, if appropriate, data from survivors were compared to nonsurvivors to identify potential prognostic indicators. Results: Thirty-six cases, 26 mature horses and 10 foals with intestinal HA were identified. Case histories included diarrhoea, colic and neurological signs and the most common clinical diagnosis was colitis and/or enteritis. The most common clinical and laboratory abnormalities included tachycardia, increased packed cell volume, hyperlactataemia and hyperglycaemia. Fourteen horses (39%) survived to discharge; NH4+ concentration on admission was the only parameter significantly associated with survival. All surviving horses and foals for which follow-up information was available recovered completely and returned to their intended use without further complications. Conclusions and potential relevance: Intestinal HA occurs in mature horses and foals and can be associated with severe clinical and laboratory abnormalities; further studies are required to investigate predisposing factors and delineate possible differences in aetiologies.