Airspace Disease

Abstract

The purpose of this chapter is to demonstrate the appearance of airspace disease in the lungs. The pulmonary acinus is the basic structural unit of the lung involved in gas exchange (Fig. 13.1). It is the structural unit of lung distal to the terminal bronchiole, is supplied by respiratory bronchioles, and is 6–10 mm in diameter. It contains alveolar ducts and alveoli. The terminal bronchiole is the most peripheral airway that is purely conductive in function with no gas exchange capability. A pulmonary lobule (or secondary pulmonary lobule) is the smallest unit of lung surrounded by connective tissue septa. One lobule contains between 3 and 25 acini. Recall the four densities seen on a radiograph – air, soft tissue, fat, and bone. Disease within the airspace is manifest on the radiograph as soft tissue density. Disease may involve numerous acini or spread from one acinar unit to another. The opacified acini become confluent, producing a fluffy, homogeneous radiographic pattern characteristic of airspace disease as seen in Fig. 13.2.