Round atelectasis is a form of lung collapse in which the atelectatic lung appears as a solitary pulmonary nodule. This type of atelectasis is due to pleural disease, usually asbestos exposure. The nodule is always adjacent to a thickened surface. Pleural thickening compresses the lung which rolls up into a ball and drags pulmonary vessels with it. These vessels are seen on the radiograph as a curved tail extending from the round atelectasis toward the hilus. The trail of thickened pleura, a pleural based nodule, and a tail extending toward the hilus are characteristic of round atelectasis.
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