Polyp formation by experimental tubal occlusion in the rat

The purpose of this study was to show the early stages of polyp formation, as part of our studies on the pathogenesis of nasal polyps. Two and 4 weeks after experimental tubal occlusion in 18 Wistar rats, 13 showed signs of bacterial infection, respective acute otitis media. In the majority of these rats polypouslike protrusions of the middle ear mucosa were found in whole-mount specimens. All polypouslike protrusions were investigated by cross sections, which revealed localised accumulation of fluid and inflammatory cells in the lamina propria. The polyps were covered with a flattened epithelium, compared to the epithelium in the surroundings. In some of the bigger polyps the apical part was without epithelial covering. The findings suggest that the epithelium by fast polyp growth may be distended and may burst, or that a primary epithelial defect has not been sufficiently covered.