Significant changes occur in the ultrasonographic appearance of the lungs in horses following exploratory celiotomy

General anesthesia for short periods of time in healthy horses for elective procedures produces minimal ultrasonographic changes in the lungs, but the effect of general anesthesia for exploratory celiotomy in horses has not previously been investigated. The objective of this study was to identify the degree of ultrasonographic changes in the lungs of horses following exploratory celiotomy and to identify risk factors that could increase the magnitude of change. 63 horses ≥ 2 years of age undergoing exploratory celiotomy were initially enrolled in a prospective observational study. Signalment, weight, exam findings and clinicopathologic data, surgical lesion and procedure were recorded for all horses. For survivors, time recumbent, laterality in recovery and presence of reflux or feed on the endotracheal tube in recovery were recorded. Thoracic ultrasonography (TUS) was performed pre- and 1, 3, and 5 days post-operatively on survivors. Linear mixed model with Bayesian estimation was used to explore day and group's effects on TUS scores, and significance level was set at 0.05. 82.5% (n = 52/63) horses survived surgery, and pre-operative TUS score was not associated with survival. Median Day 1 TUS scores (25.94, 95% CrI: 10.47-41.50), were significantly higher than pre-operative scores (21.19, 95% CrI: 9.75-32.50). Magnitude of change in TUS score from the pre-operative exam to Day 1 was significantly associated with the presence of feed on the endotracheal tube at the time of extubation (P = 0.03) and reflux in recovery (P = 0.006). Significant changes occur in the ultrasonographic appearance of the lungs the day following exploratory celiotomy, but appear to be self-limiting.