[Value of bronchoalveolar lavage in the diagnosis and management of diffuse interstitial fibrosing lung diseases].

Bronchoalveolar lavage (BAL) is an exploratory technique which is easy to perform and collect cellular constituents, notably inflammatory and immunocompetent cells, as well as biological elements that are present in the distal airways. In patient with chronic diffuse infiltrative lung disease, analysis of these parameters reveals various disturbances such as neutrophilia frequently associated with eosinophilia and, in some cases, lymphocytosis. These features are not specific, but they differentiate chronic diffuse infiltrative lung diseases from sarcoidosis and hypersensitivity lung diseases. Alveolar inflammation (alveolitis) correlates with the evolutive potential of the lesions and their ability to respond to treatment. The presence of lymphocytosis is usually associated with response to corticosteroid therapy, whereas the presence or persistence of neutrophilia and, even more, eosinophilia is characteristic of patients who do not respond to corticosteroids but are amenable to the cyclophosphamide-corticosteroid combination. BAL therefore increasingly appears as an irreplaceable tool to understand the physiopathology of chronic diffuse infiltrative lung diseases.