Perspectives in veterinary medicine: Description and classification of bronchiolar disorders in cats

Reinero, Carol R.; Masseau, Isabelle; Grobman, Megan; Vientos-Plotts, Aida; Williams, Kurt

Compared to humans, cats lack connective tissue septa in the lung outlining a secondary pulmonary lobule (Box 1). Furthermore, there is no distinctive recognizable pattern of analogous bordering venules and lymphatics arranged in discrete polyhedral shapes that might comprise this unit. Thus, even in disease, pathology on CT scans of cats would not reflect distribution around a pulmonary lobule. Terms used in imaging of human lung such as centrilobular, panlobular, interlobular, and intralobular are not appropriate descriptors in cats. Dogs are similar to cats and also lack secondary pulmonary lobules, and the pulmonary acinus has been suggested to be the important highresolution CT (HRCT) unit of the canine lung. 26 The acinus is defined as the region of the lung supplied by a single terminal bronchiole, representing the smallest functional unit of the lung. Because it is smaller than the secondary pulmonary lobule that is the smallest visible structure on HRCT, we believe that the pulmonary acinus is not a replaceable term as the important HRCT unit of the feline (or canine) lung. Instead, descriptors of collective changes of multiple acini visible on HRCT will need to be developed and refined.