Rounded atelectasis

Imaging description Rounded atelectasis has four key imaging features [1–3] (Figures 26.1 and 26.2). (1) The primary finding is a rounded, mass-like region of consolidation. Air-bronchograms are a common finding within the mass and the portion closest to the hilum typically has irregular margins. (2) The focus of rounded atelectasis should abut a pleural abnormality. Most commonly this is an area of pleural thickening. Pleural calcification can be seen. (3) There is a swirl of vessels and bronchi leading into the mass; the so-called “comet-tail sign.” (4) There should be evidence of volume loss within the affected lobe commensurate to the size of the “mass.” Importance Rounded atelectasis is a relatively frequent finding and the distinction from primary malignancy is important. When all four findings listed above are present the diagnosis can be made and no further workup is necessary.