Draped aorta sign | Radiology Signs

Answer:

The draped aorta sign indicates a contained or chronic contained rupture of an aortic aneurysm. On axial CT the posterior wall of the aneurysm loses its normal convex contour and instead conforms to, and appears to drape over, the anterior surface of the adjacent vertebral body. Two features define it: the posterior aortic wall cannot be identified as a distinct line separate from the spine, and the normal fat plane between the aorta and the vertebral column is effaced. Associated findings include vertebral body erosion or scalloping, focal discontinuity of mural calcification, periaortic stranding and a hyperattenuating crescent. Because the aneurysm is held together only by adventitia, periaortic fibrosis and the vertebral column, the sign identifies a lesion that has already ruptured and is at high risk of catastrophic free rupture, so it should be treated as a surgical emergency even when the patient is haemodynamically stable and pain-free.

Why is it called so?

The aneurysm sac loses its own posterior contour and hangs over the vertebral body like a drape or cloth thrown over a support.

Pathophysiology

Progressive aneurysmal degeneration erodes the posterior aortic wall against the spine. When the wall gives way, bleeding is contained by the retroperitoneal tissues, the vertebral column and the surrounding fibrotic reaction rather than escaping freely. The residual sac therefore has no structural posterior wall of its own and simply moulds to the bony surface behind it, obliterating the intervening fat plane. Continued pulsatile pressure against the vertebral bodies produces the associated erosions seen in chronic contained rupture.

Alternative names: Aortic drape sign

Other associated named signs: Hyperattenuating crescent sign, focal discontinuity of intimal calcification, and the tangential calcium sign

References

1. Fonseca EKUN, E Castro ADA, Tames AVC, Jayme EM, Paiva OA, Sokolowski LR. The draped aorta sign of impending aortic aneurysm rupture. Abdom Radiol (NY). 2017;42(8):2190-2191. PMID: 28337519.