Radiographic manifestations of lobar atelectasis.

In this article we review the plain radiographic and computed tomographic manifestations of lobar atelectasis. The progression of lobar atelectasis from mild to marked volume loss is emphasized. Common combinations of lobar and whole lung atelectasis are also discussed. Radiographic features that help distinguish lobar atelectasis from pleural thickening, pleural effusion, and mediastinal masses are outlined. Where appropriate, selected examples of segmental atelectasis are also presented. The recognition of lobar atelectasis is important, particularly in cases stemming from obstructing endobronchial tumors. Since all signs of volume loss are not present in any given case, knowing as many signs of lobar atelectasis as possible is useful. Careful analysis of the chest radiograph and subtle alterations in the fissures and hilar vascularity aids in differentiating lobar atelectasis from other intrathoracic processes.