Etiology andClassification

The classification of ILDs is somewhat hampered by the plethora of pathologies that can manifest as an ILD pattern on radiographs (Reinero and Cohn 2007). Furthermore, ILDs can be described as diffuse or nodular. Generally, nodular patterns are more con­sistent with neoplastic diseases with fungal disease, eosinophilic lung diseases and car­diogenic lung edema in cats serving as other possible differential diagnoses. Finding a nodular lung pattern on a radiograph typi­cally necessitates the exclusion of neoplasia, and ultrasound guided fine-needle aspirates are useful to achieve this. Diffuse ILDs can result from a number of pathophysiological processes such as immune mediated/allergic, infectious, toxicological, parasitic, idiopathic, and, more rarely, neoplastic disease.