Conclusion

The external ear canal of a dog is lined with tissue that in many ways is very simi­lar to normal epidermis and dermis elsewhere on the body. However, tissue response to inflammatory stimuli is unique to the ear canal.

Important breed differences in histopathology support clinical observations that American Cocker Spaniels have more severe otic disease than any other breed. Although Cocker Spaniels are less likely than other breeds to exhibit severe fibrosis of the ear canal, they have a demonstrated predisposition for ceruminous gland ecta­sia, proliferative ceruminous gland hyperplasia, osseous metaplasia, and lipofuscin­containing macrophages. These changes result in increased risk for end-stage otitis externa requiring total ear canal ablation surgery. In fact, Cocker Spaniels are 24 times more likely to require this surgery than any other breed and 14 times more likely than would be predicted based on breed popularity.

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