CT scan of left lower lobe atelectasis

Chronic complete lobar atelectasis of the left lower lobe. Triangular opacity in left paraspinal location (arrow) obscures the lateral contour of the descending aorta. Cylindrical bronchiectasis is seen in the affected lobe and accounts for the multiple small lucencies permeating the atelectatic left lower lobe. These findings are the result of necrotizing pneumonia in the patient's distant past.