Left lower lobe atelectasis due to pleural effusion

Left lower lobe compressive atelectasis of the basal segments due to a left pleural effusion that resulted after esophageal perforation during endoscopy. Axial computed tomography (CT) scan shows the collapsed basal segments of the left lower lobe (arrow) with accompanying pneumomediastinum (dashed arrow) and extravasation of water-soluble contrast material after an esophagram (thick arrow).