Detection of silent reflux events by nuclear scintigraphy in healthy dogs

Abstract

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 99m-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). 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.