Thoracic radiography, bronchoalveolar lavage cytopathology, and pulmonary parenchymal histopathology: a comparison of diagnostic results in 11 cats.

The purpose of this study was to compare the diagnostic results and value of thoracic radiography, bronchoalveolar lavage (BAL) fluid cytopathology, and lung histopathology in 11 cats with spontaneous respiratory disease in which radiography and cytopathology were inadequate in establishing a definitive diagnosis. In these cats, radiographic patterns were characterized as bronchial (n=6), interstitial (n=3), and alveolar (n=2); other features included hyperinflation (n=3), bronchiectasis (n=2), pleural fissure lines (n=2), pulmonary nodules (n=2), atelectasis (n=1), and a tracheal mass (n=1). Bronchoalveolar lavage fluid was unremarkable in two cats. Abnormal BAL fluid showed inflammation (n=5), hemorrhage (n=2), epithelial hyperplasia (n=1), or was suspicious for neoplasia (n=1). Histopathological evaluation revealed inflammation (n=8), neoplasia (n=2), and vascular congestion (n=1). The predominant radiographic location of disease correlated with the same histopathological location in seven cats, and the cytopathological class of BAL fluid was consistent with the histopathological class of disease in seven cats. There was poor correlation between the types of cells found in the BAL fluid and the pathologist's prediction of the types of cells likely to be found in the BAL fluid based on the amount and type of airway cellularity seen on histopathological examination. The results of this study suggest that in some cats, BAL fluid cytopathology does not always correlate with the type of pulmonary disease identified on histopathology. In respiratory diseases where radiography and cytopathology fail to provide a definitive diagnosis, histopathological examination of the lung may be necessary.