Ductus diverticulum mimicking ductus arteriosus aneurysm

Imaging description Ductus diverticulum (DD) is an anatomic variant incidentally found at cardiovascular imaging characterized by a smooth bulge of the anterior wall of the aorta at the aortic isthmus, just distal to the origin of the left subclavian artery. DD is best visualized on sagittal oblique reconstructions on CT, MRI, or digital subtraction angiography (DSA) (Figures 57.1 and 57.2). DD may be difficult to appreciate on standard axial images. On reconstructions, it is recognized as an anteriorly directed bulge of the undersurface of the aortic arch that extends to the proximal descending thoracic aorta. DD has smooth, gentle margins, and obtuse shoulders. Importance DD must not be confused with traumatic aortic transection or ductus arteriosus aneurysm, both of which can occur at the same location and have a greater risk of morbidity and mortality. Typical clinical case scenario DD is typically encountered as an incidental finding on CT, MR or DSA and is of no clinical significance. It occurs in approximately 26% of adults and requires no follow-up or treatment. Differential diagnosis Traumatic aortic transection, also known as post-traumatic pseudoaneurysm, is found in patients with a history of highvelocity trauma. At cross-sectional imaging, aortic transections arise from the anterior wall of the aorta at the isthmus, similar to DD. However, aortic transections have acute angles with the aortic wall, are irregular in shape and size, and often have a visible intimal flap (Figure 57.3). There may be a narrow neck that communicates with the aorta. Associated periaortic and mediastinal hematoma are typically present with traumatic aortic transection. Aneurysm of the ductus arteriosus is a rare entity characterized by a saccular aneurysm of the undersurface of the aortic arch in the region of the ductus arteriosus (Figure 57.4). Wall calcifications and partial thrombosis are frequently present. Some believe this entity is due to incomplete obliteration of the patent ductus arteriosus during early development that results in a blind-ending stump communicating with the aortic lumen. Progressive enlargement occurs over years.