Serum and Fecal 3-Bromotyrosine Concentrations in Dogs with Chronic Inflammatory Enteropathy: Clinical Parameters and Histopathological Changes

SIMPLE SUMMARY: This study aimed to examine the diagnostic sensitivity of 3-bromotyrosine (3-BrY) and compare serum and fecal 3-BrY concentrations between dogs with chronic inflammatory enteropathy (CIE) that showed pathological changes in biopsy samples of the gastrointestinal (GI) tract. A weak correlation was found between serum C-reactive protein and serum 3-BrY concentrations, but no correlation was observed between the canine chronic enteropathy clinical activity index and serum or fecal 3-BrY concentrations. No significant difference in 3-BrY concentrations was found in biological samples between dogs with CIE who had various GI pathological changes. It is worth noting that dogs with CIE often have increased 3-BrY concentrations in both their serum and fecal samples. However, these 3-BrY elevations may not accurately reflect the severity of GI histological findings. ABSTRACT: Chronic inflammatory enteropathies (CIEs) in dogs involve the infiltration of gastrointestinal tissue with inflammatory cells. This study aimed to assess the sensitivity of serum and fecal 3-bromotyrosine (3-BrY) concentrations in dogs with CIE. The difference in 3-BrY concentrations in dogs with different gastrointestinal (GI) pathological changes was also assessed. In total, 68 dogs with CIE were enrolled in the study. The median serum 3-BrY concentration was 3.3 µmol/L, while the median 3-day mean and maximum fecal 3-BrY concentrations were 38.9 and 63.2 mmol/g of feces, respectively. The median serum C-reactive protein concentration was 45.0 mg/L. The median 3-day mean and maximum fecal α(1)-proteinase inhibitor concentrations were 6.1 and 9 µg/g of feces, respectively. Increased 3-BrY concentrations were observed in 90.9% of CIE dogs based on serum concentrations, 75.8% based on mean fecal concentrations, and 69.4% based on maximum fecal concentrations. A weak correlation (ρ = 0.31, p < 0.0118) was found between serum CRP and serum 3-BrY concentrations. There was no correlation between the canine chronic enteropathy clinical activity index and serum or fecal 3-BrY concentrations (p > 0.05). Additionally, no significant difference in serum or fecal 3-BrY concentrations was found among CIE dogs with different GI pathological changes (p > 0.05). In conclusion, dogs with CIE have increased 3-BrY concentrations in serum and fecal samples. However, 3-BrY concentrations may not accurately indicate the severity of gastrointestinal inflammation.