Correct!
4. Thoracic CT shows extensive low attenuation throughout the lung parenchyma
The thoracic CT shows multifocal areas of low attenuation throughout the lung parenchyma, but the low attenuation areas do not represent true cysts- they do not have “walls” as cysts typically possess. Rather, the low attenuation in the apices has a somewhat “punched-out” appearance, whereas the basal low attenuation is more diffuse appearing. In the bases, at first glance, the lung parenchyma may appear relatively normal. However, on closer inspection, there are relatively fewer vessels seen in the bases than expected, and the vessels appear small, stretched, attenuated, and more separated from each other than usual. The airway walls may appear somewhat thickened, but they are not abnormally dilated. The peripheral pulmonary arteries do not appear enlarged; rather, they actually appear smaller than normal. There is no evidence of interlobular septal thickening to suggest increased pressure edema. Air trapping is typically difficult to diagnosis on inspiratory scans alone. Usually one reviews post-expiratory scans to observe the lack of appropriate increase, or the paradoxical decrease, in lung parenchymal attenuation on post-expiratory imaging, compared with inspiratory imaging, to diagnose air trapping. However, one can occasionally suggest the presence of air trapping on an inspiratory examination when mosaic perfusion is present- areas of inhomogeneous lung attenuation, often with a geographic appearance. When air trapping produces mosaic perfusion (as opposed to the much rare vascular obstructive causes, like pulmonary hypertension, pulmonary emboli, and obliterative thrombotic microangiopathy), the vessels often appear smaller in the more lucent regions and somewhat larger in the denser regions of lung], and areas of distinct lobular low attenuation may also be evident. In this case, the low attenuation in the bases appears lobular, but it is diffuse rather than geographic in distribution.
Additional history was performed and the patient admitted to smoking 2-3 cigarette packs per day for the previous 15 years.
Based on the information thus far, what is the most likely diagnosis? (Click on the correct answer to proceed to the sixth of seven panels)