Urinary Leukotriene E4 Concentrations as a Potential Marker of Inflammation in Dogs with Inflammatory Bowel Disease

Background Inflammatory bowel disease (IBD) and food‐responsive diarrhea (FRD) are chronic enteropathies of dogs (CCE) that currently can only be differentiated by their response to treatment after exclusion of other diseases. In humans, increased urinary concentrations of leukotriene E4 (LTE4) have been associated with active IBD. Objectives To evaluate urinary LTE4 concentrations in dogs with IBD, FRD, and healthy controls, and to assess correlation of urinary LTE4 concentrations with the canine IBD activity index (CIBDAI) scores. Animals Eighteen dogs with IBD, 19 dogs with FRD, and 23 healthy control dogs. Methods In this prospective study, urine was collected and CIBDAI scores were calculated in client‐owned dogs with IBD and those with FRD. Quantification of LTE4 in urine was performed by liquid chromatography‐tandem mass spectrometry and corrected to creatinine. Results Urinary LTE4 concentrations were highest in dogs with IBD (median 85.2 pg/mg creatinine [10th–90th percentiles 10.9–372.6]) followed by those with FRD (median 31.2 pg/mg creatinine [10th–90th percentiles 6.2–114.5]) and control dogs (median 21.1 pg/mg creatinine [10th–90th percentiles 9.1–86.5]). Urinary LTE4 concentrations were higher in dogs with IBD than in control dogs (P = .011), but no significant difference between IBD and FRD was found. No correlation was found between urinary LTE4 concentrations and CIBDAI. Conclusions and Clinical Importance The higher urinary LTE4 concentrations in dogs with IBD suggest that cysteinyl leukotriene pathway activation might be a component of the inflammatory process in canine IBD. Furthermore, urinary LTE4 concentrations are of potential use as a marker of inflammation in dogs with CCE.