Effects of acidic and nonacidic reflux on the eustachian tube: An animal experiment.

We investigated the effects of pepsin/hydrochloric acid and bile acids on eustachian tube function and eustachian tube mucosa in 40 Sprague-Dawley rats. The animals were randomly assigned to groups of 10: one group received pepsin/hydrochloric acid (pepsin/HCl group), another received human bile (human bile group), a third received a mixture of pepsin/HCl and human bile (combination group), and the fourth received isotonic saline solution (control group). Test solutions were applied transnasally three times a day for 10 days. Passive opening pressures and passive closing pressures were measured digitally at baseline and then on days 3, 5, and 10. After 10 days, the rats were sacrificed and histologic changes in the eustachian tube mucosa were analyzed. At study's end, we observed that the increases in passive opening pressures and passive closing pressures in all three experimental groups were significantly greater than those of the control group. Moreover, the increases in passive opening and closing pressures were significantly greater in the combination group than in both the pepsin/HCl and the human bile groups. In the tympanic orifice, the degree of lymphocyte and polymorphonuclear leukocyte infiltration was significantly higher in all three experimental groups than in the control group. In the nasopharyngeal orifice, lymphoid follicle formation was significantly more common in the human bile group than in the control group; also, the presence of subepithelial vasodilation and subepithelial edema was significantly more common in the pepsin/HCl and combination groups than in the controls. Of the three experimental solutions tested, the combination of pepsin/HCl and human bile was the most injurious to eustachian tube function. Reflux of bile acids causes eustachian tube dysfunction, and this damage worsens with the introduction of an acidic compound.