In our present study, laryngeal granuloma seems to have
developed by the combined effect of mechanical injury of
the vocal cord mucosa and gastric acid reflux. However,
the incidence of laryngeal granuloma is rare when compared
with the high prevalence of GERD.8 Furthermore,
not all the rats with GERD developed laryngeal granuloma:
we speculate that either gastric acid reflux or mechanical
injury of the vocal cord mucosa was not sufficient to cause
the development of laryngeal granuloma in some of the
experimental rats. In our previous study,2 the severity of
esophagitis and the histological changes in the larynx differed.
Therefore, we cannot exclude the possibility that a
factor(s) other than mechanical injury and gastric acid
reflux facilitates the development of laryngeal granuloma.
To investigate this factor(s), a longer period of observation
of the GERD-model rats is necessary. Future studies should
also address how the histological changes observed in the
rat larynx are associated with the degree of gastric acid
reflux.
Conclusions
In this study, the rat model of GERD with mechanically
injured vocal cord mucosa developed laryngeal granuloma,
which appeared to be similar to human laryngeal granuloma.
The results suggest that the development of laryngeal
granuloma may involve both mechanical injury and gastric
acid reflux.
Acknowledgments
We thank Ms Sawa Tanaka, Saga University, for her valuable
assistance in the tissue preparations.
Authors’ Note
The experiments were conducted in accordance with the guidelines
of the Ethical Committee of Experimental Animal Care of
Saga University.
Figure 5. Histopathological structure of human laryngeal
granuloma. Original magnification, 100 H&E staining.