Emphysema is an important disease in humans; however, in other animals it typically occurs as a result of another lung disease. The condition leads to difficulty in expelling air from the lungs, making breathing more difficult. Two major forms of emphysema are generally recognized. Alveolar emphysema is abnormal permanent enlargement of the alveoli, which are small air sacs deep in the lungs. Interstitial emphysema is the presence of air within the supporting connective tissue of the lung. Chronic obstructive pulmonary (lung) disease (COPD) can cause enlargement and destruction of air spaces. The association of high numbers of white blood cells with COPD suggests that there may be allergic, infectious, and/or toxicologic causes for the condition. Congenital lobar emphysema of dogs (a condition seen in the Pekingese breed) occurs because of incomplete development of the bronchiolar cartilage.

Last full review/revision July 2011 by Ned F. Kuehn, DVM, MS, DACVIM; Neil W. Dyer, DVM, MS, DACVP; Joe Hauptman, DVM, MS, DACVS; Steven L. Marks, BVSc, MS, MRCVS, DACVIM; Stuart M. Taylor, PhD, BVMS, MRCVS, DECVP