Rethinking Pulmonary Fibrosis in Dogs and Cats

“Idiopathic pulmonary fibrosis (IPF)”, a term applied to a devastating and ultimately fatal disorder in dogs and cats, is currently used to encompass all types of fibrosis in these species.  Pulmonary fibrosis in dogs and cats is not a single homogenous disease, nor is it necessarily idiopathic. Its name derives from IPF in humans, the most common of all fibrosing lung disorders. IPF requires multidisciplinary collaboration and well-defined criteria including exclusion of other interstitial lung diseases and the presence of a computed tomographic (CT) or histologic pattern known as usual interstitial pneumonia (UIP).  Fibrosis represents a response to injury; knowledge of the type of injury has key implications for disease management.  This lecture will focus on providing a foundation for understanding the patterns of fibrosis seen on histologic examination and what clues they provide to the inciting insult (e.g., inhalational damage, hematogenous insults, etc).  An approach for a thorough evaluation inclusive of clinical, imaging, laboratory and pathologic data will be provided in a case-based fashion. Importantly, while end-stage fibrotic lung has no viable treatment, recognition of known triggers of fibrosis earlier in the course of disease could provide novel means for targeted therapy.