Detection of silent reflux events by nuclear scintigraphy in healthy dogs

Background Reflux and aspiration in people are associated with respiratory disease, whereas approximately 50% of healthy adults microaspirate without apparent consequence. In dogs, analogous information is lacking. Hypothesis Healthy dogs commonly have gastroesophageal reflux and a proportion of these dogs will have laryngopharyngeal reflux with silent aspiration. Animals Twelve healthy, client‐owned dogs. Methods Prospective study: Dogs were free‐fed a meal containing (111 MBq) colloidal 99 m‐technetium phytate. Dynamic‐scans were performed 5 and 30 minutes postingestion. Time‐activity curves, reflux margination, volume, frequency, and duration were evaluated over 7 regions of interest in dorsal ± left‐lateral recumbency. Static scans (dorsal recumbency) were performed 2 and 18 hours postfeeding to detect aspiration. Reflux and aspiration were defined as counts ≥200% background activity ± decreased gastric counts. Between‐group comparisons were performed by Wilcoxon rank‐sum test or one‐way ANOVA on ranks with significance of P  < .05. Results In this study, reflux of variable magnitude was detected in 12/12 dogs. No significant differences in outcome parameters were detected with recumbency ( P  > .05). Margination to the pharynx and proximal, middle, and distal esophagus was identified in 5/12, 2/12, 3/12, and 2/12 dogs, respectively. Median (IQR) reflux frequency and duration were 2 events/5 minutes (1‐3.3 events/5 minutes) and 6 seconds (4‐9 seconds) respectively. No dog had detectable aspiration. Conclusions and Clinical Importance Nuclear scintigraphy can document reflux in dogs. Reflux, but not aspiration, is common in healthy dogs and must be considered when interpreting results in clinically affected dogs.