Emphysema classification

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mehrian Jafarizade, M.D [2]

Emphysema can be classified by location in to different types such as panacinary, centroacinary, congenital lobaremphysema, and paraseptal emphysema.

Emphysema can be classified by location into three categories:

• The entire respiratory acinus, from respiratory bronchiole to alveoli, is expanded. Occurs more commonly in the lower lobes (especially basal segments) and in the anterior margins of the lungs.^[1]

• The respiratory bronchiole (proximal and central part of the acinus) is expanded. The distal acinus or alveoli are unchanged. Occurs more commonly in the upper lobes.^[1][2]

CLE results in over-expansion of a pulmonary lobe, and resultant compression of the remaining lobes of the ipsi-lateral lung (and possibly also the contralateral lung). There is bronchial narrowing because of weakened or absent bronchial cartilage.^[3] There may be congenital extrinsic compression, commonly by an abnormally large pulmonary artery. This causes malformation of bronchial cartilage, making them soft and collapsible.^[3] CLE is a potentially reversible (yet possibly life-threatening) cause of respiratory distress in the neonate.^[3]

Para-septal emphysema is a type of emphysema which involves the alveolar ducts and sacs at the lung periphery. The emphysematous areas are sub-pleural in location and often surrounded by inter-lobular septa (hence the name). It may be an incidental finding in young adults, and may be associated with spontaneous pneumothorax. It may also be seen in older patients with centri-lobular emphysema. Both centri-lobular and para-septal emphysema may progress to bullous emphysema. A bulla is defined as being at least 1 cm in diameter, and with a wall less than 1 mm thick. Bullae are thought to arise by air trapping in emphysematous spaces, causing local expansion.^[4]

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