Venous blood lactate concentration as a predictor of intestinal viability in horses with acquired indirect inguinal hernia

Abstract Background Acquired indirect inguinal hernia represents a life‐threatening emergency. Therapeutic decision‐making largely depends on intestinal viability, for which specific predictive parameters (such as venous lactate) have not been evaluated. Objectives Investigating the predictive performance of venous blood lactate and other laboratory results on intestinal viability in horses with acquired indirect inguinal hernias. Study Design Retrospective multicentre observational study. Methods Seventy‐four horses diagnosed with acquired indirect inguinal hernia (treated surgically) at two referral hospitals between 2007 and 2025 were classified considering intraoperative intestinal viability using Freeman's grading score. Group comparisons regarding laboratory results at admission were performed. Normality was assessed (Kolmogorov–Smirnov) and results are presented as mean ± standard deviation when its assumption was met, and median [interquartile range] when not. T ‐test or Mann–Whitney U ‐test were performed as appropriate. Receiver operating characteristic curve analysis and logistic regression modelling were evaluated. Results Seventy‐four horses were included. Intestinal viability was confirmed in 39 horses (53%), and non‐viability in 35 horses (47%). Survival to discharge was significantly higher in the viable group (92% [36/39] vs. 74% [26/35]; p = 0.036). Venous blood lactate concentrations were significantly higher in the non‐viable group (4.9 [3.2, 8.6] mmol/L vs. 1.6 [1.2–2.9]; p < 0.001), demonstrating excellent discriminative ability (AUC = 0.833; [95% CI 0.739–0.928]). Youden's cut‐off value of ≥3.2 mmol/L yielded a sensitivity of 77% [95% CI 61%–87.9%], and specificity of 84.6% [95% CI 70.3%–92.8%]. Blood urea nitrogen was significantly higher in the non‐viable group (18.9 ± 9.2 mg/dL vs. 14.3 ± 6.2 mg/dL; p = 0.029). It showed limited predictive performance (AUC = 0.652; [95% CI 0.509–0.795]). A binary logistic regression model combining both did not improve the venous lactate individual one. Main Limitations Retrospective design, incomplete availability of clinical variables, moderate sample size. Conclusions Venous blood lactate could predict intestinal devitalisation in horses with acquired inguinal hernias and assist preoperative decision‐making.