Bibasilar airspace disease, also known as alveolar lung disease, is a condition of the lungs in which the air spaces are swollen and contain fluid. The main causes are infection and aspiration. Less common causes include bleeding or protein secretions within the lungs.
The term "bibasilar" indicates that the location of the condition is on both sides and in the lower portion of the lungs. Airspace refers to the alveoli, which are air sacs that aid in oxygen exchange. The word "disease" refers to the presence of fluid and swelling in the alveoli. Bibasilar airspace disease can be diagnosed through a chest X-ray.