Pre- and post-operative plasma histamine concentrations in 35 dogs with mast cell tumours

This study aims to determine if plasma histamine concentrations (PHCs) reduced following mast cell tumour (MCT) removal and to further confirm that dogs with MCTs have higher PHCs compared to healthy dogs. Blood samples were taken pre-operatively and 2 to 4 h post-operatively in 35 dogs with cytologically confirmed MCTs undergoing removal and ten control dogs undergoing ovariohysterectomy. An enzyme immunoassay was used to determine the PHC. There was no statistically significant difference in the change in PHCs in dogs with MCTs compared to the control dogs undergoing ovariohysterectomy. It was confirmed that dogs with MCTs have higher PHCs compared to normal dogs. This study showed that dogs with MCTs had statistically significant hyperhistaminemia compared with the control dogs. This could lead to gastroduodenal ulceration which may be subclinical or cause clinical signs such as vomiting, diarrhea, or anemia and supports the use of H₂ receptor antagonist drugs pre-operatively. Despite the rapid metabolism of histamine, abdominal surgery causes ongoing and sustained histamine release which increased plasma concentrations. Blood sampling at a later stage post-operatively may have yielded different results.