Congenital lung malformations in infants A variety of congenital lung malformations arise from aberrations in different stages of lung

The earliest signs of lung development occur around four weeks after conception with the appearance of a bud (the tracheal diverticulum) from the primitive foregut. Lung development can be described in four stages, embryonic, glandular, canalicular and sacular (TABLE 1). Towards term more subtle changes in the structure of the terminal airspaces, including elastin deposition and septation, which result in the formation of alveoli, greatly increase the surface area available for gas exchange. This process continues after birth until around eight years of age. Although the aetiology of congenital lung malformations is unknown these abnormalities probably arise from prenatal airway obstruction during the embryonic and glandular stages of lung development. It seems likely that the nature of the malformation is determined by the gestational age at which obstruction occurs.