Fasting Serum Bile Acid Profiles in Dogs with Food-Responsive and Immunosuppressant-Responsive Chronic Inflammatory Enteropathy: An Exploratory LC–MS/MS Study

Bile acid (BA) dysmetabolism is implicated in canine chronic inflammatory enteropathy (CIE), but fasting serum profiles across treatment-response groups remain poorly characterized. This exploratory observational study analyzed pretreatment serum from dogs subsequently classified as food-responsive enteropathy (FRE; n = 8) or immunosuppressant-responsive enteropathy (IRE; n = 5), with four unmatched purpose-bred Beagle controls. Targeted LC–MS/MS, performed using a published canine serum method, provided results for 15 BA species. All samples were analyzed in one batch by an analyst blinded to subsequent group assignment. Eight species quantifiable in every dog and ten derived variables were compared using Kruskal–Wallis tests with Benjamini–Hochberg correction across 18 omnibus tests. Cholic acid and unconjugated primary BA concentrations were higher in IRE than in controls and FRE. The total primary-to-secondary BA ratio showed a monotonic group ordering (control < FRE < IRE; H = 13.76, p = 0.0010, q = 0.0092; epsilon-squared = 0.840), with all Bonferroni-corrected pairwise comparisons significant. A post hoc four-scenario sensitivity analysis comprising the submitted zero-substitution analysis and three LOD/LOQ-based alternatives reproduced the same 18-test FDR-significant set and the same ratio inference. This analysis tests robustness to censored-value handling but is not independent validation. The findings suggest group-associated serum BA patterns, but the small sample, clinical heterogeneity, and unmatched controls preclude diagnostic or treatment-predictive interpretation.