“…A thoracic aortic aneurysm is considered "unstable" when it is rapidly enlarging or shows signs of rupture or imminent rupture, such as a high-attenuation crescent within the aortic wall on unenhanced CT images, reflecting intramural hematoma. In addition, other findings of a rupture include focal discontinuity of intimal calcifications, eccentric shape of the aorta, and a "draped" aorta, which is defined as an indistinct margin of the posterior aortic wall from the adjacent vertebral body (32). Rupture of a descending aortic aneurysm usually occurs into the mediastinum and the left pleural space, producing periaortic soft-tissue hematoma, hemothorax, pleural or pericardial effusion, or even a contrast blush of active extravasation at the site of rupture (32,33).…”