ground glass opacity
The term ground glass opacity was first described on CT of the chest and refers to an increase in lung attenuation that does not obscure the pulmonary vasculature. This is in contrast to consolidation which obscures underlying bronchovascular anatomy and appears much more opaque. Like consolidation, ground glass opacity can be focal, multifocal, or diffuse and can be seen in acute or chronic conditions. It can be caused by partial filling of airspaces, interstitial thickening, decreased lung aeration, and/or an increase in capillary blood volume. There is no direct correlate of ground glass opacity on chest radiographs. Paradoxically, some patients with ground glass opacity on CT examination will have chest radiographs that appear normal, whereas others will appear as consolidation and yet others will appear as a faint increased opacification of the lungs.