Rounded atelectasis 2021-02-24T13:51:58Z Helical atelectasis See Figure 65 of Hansell DM, et al., Fleischner Society: glossary of terms for thoracic imaging. Radiology. 2008;246:697-722. Rounded atelectasis is rounded collapsed lung associated with invaginated fibrotic pleura and thickened and fibrotic interlobular septa. Most frequently, it is the consequence of an asbestos-induced exudative pleural effusion with resultant pleural scarring, but it may occur with any cause of pleural fibrosis. On chest radiographs, rounded atelectasis appears as a mass abutting a pleural surface, usually in the posterior part of a lower lobe. Distorted vessels have a curvilinear disposition as they converge on the mass (the comet tail sign). The degree of lobar retraction depends on the volume of atelectatic lung. It is almost invariably associated with other signs of pleural fibrosis (eg, blunting of costophrenic angle). CT is more sensitive for the detection and display of the characteristic features of rounded atelectasis. An additional sign is homogeneous uptake of contrast medium in the atelectatic lung. Comet tail sign Pleural pseudotumor Blesovsky syndrome Folded lung syndrome Pleuroma Atelectasis