CTICasesLeft Lower Lobe Atelectasis secondary to Bronchial Carcinoid
Imaging findings
Frontal chest radiograph demonstrates signs of left lower lobe volume loss, including crowding of vessels, loss of the left descending thoracic aortic interface, a subtle 'sail sign' or triangular opacity behind the heart, and flattening of the left middle heart border (flat waist sign) due to mediastinal rotation. Chest CT confirms complete collapse of the left lower lobe secondary to an obstructing endobronchial carcinoid tumor with punctate dystrophic calcifications.
Key takeaways
Left lower lobe atelectasis can be highly subtle on frontal radiographs because the collapsed lobe often retracts posteromedially and merges with the cardiac silhouette. Secondary signs of volume loss—such as loss of the descending aortic interface, vascular crowding, and mediastinal shift—are critical indicators of lobar collapse, which should prompt further evaluation for a central obstructing neoplasm like a bronchial carcinoid.
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