The nasal cavity is a major portal of entry for many pathogens, with its homeostasis being constantly challenged [1]. Nasal diseases are often clinically indistinguishable from one another, as clinical signs and imaging for different conditions are similar and often non-specific [[2], [3], [4]]. Clinical signs often associated with these diseases include sneezing, stertorous breathing and nasal discharge [3], which makes it difficult to establish a definitive diagnosis without the aid of histopathology in most animals with upper respiratory disease [[5], [6], [7], [8]]. In addition, several lesions within the nasal cavity may be subclinical. With the increasing use of rhinoscopy in cats and dogs, recognizing the various histological lesions in the nasal cavity and establishing their true clinical importance is essential.

Although several authors point out the prevalence and anatomopathological aspects of various lesions in the nasal cavity of dogs and cats [[2], [3], [4], [5], [6], [7], [8], [9], [10], [11]], little is known about what to expect in the nasal cavity of apparently healthy animals. Nasal cavity exploration is not a part of conventional necropsy, and systematic studies analysing histopathological changes in the upper respiratory tract of a general population of dogs and cats are scarce to non-existent.

The objective of this study was to characterize the anatomopathological changes of the nasal cavity in dogs and cats submitted to routine post-mortem examination in a Brazilian veterinary diagnostic service.