Difference between revisions of "CT of abdominal aortic aneurysm"

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Latest revision as of 23:11, 12 July 2019

Because it is a widely available, rapid imaging method, computed tomography (CT) angiography is the exam of choice in such cases.

Findings

Early identification of imaging findings indicating the rupture or imminent risk of rupture of an AAA can change the prognosis and ensure more appropriate treatment.

Rupture

  • Retroperitoneal hematoma (most common): translates to a loss of aneurysmal wall integrity and appears on CT as a periaortic focus of soft-tissue density. The hematoma can extend into the pararenal and perirenal spaces, as well as to the psoas muscle and into the intraperitoneal space. In contrast-enhanced images, active extravasation of the contrast agent can be seen.
  • Draped aorta sign: in cases of a ruptured aneurysm contained, neighboring structures such as the vertebral bodies or adjacent retroperitoneal tissues buffer the hemorrhage and the patient may remain hemodynamically stable(1). A CT scan of a contained rupture can show the draped aorta sign, in which neither the posterior wall of the aorta nor the periaortic fat plane is distinguishable.

Imminent rupture

  • The maximum diameter and growth rate of an aneurysm are the most common predictors of its rupture, underscoring the importance of serial imaging in the follow-up of patients with an AAA. In most cases of typical fusiform aneurysms, a surgical approach is indicated if the aneurysm diameter is > 5.4 cm or the aneurysm grows by more than 5 mm over a six-month period.
  • Hyperattenuating crescent sign: corresponds to a hyperattenuating peripheral area within the wall of the aorta or within a mural thrombus, indicating infiltration of blood from the lumen of the aneurysm into those structures, with consequent weakening of the wall of the aneurysm. The hyperattenuating crescent sign is best visualized on unenhanced CT scans and is characterized by attenuation greater than that of intraluminal blood.
  • Focal discontinuity of parietal circumferential calcification: can indicate that an aneurysm is unstable. That is especially relevant when the discontinuity is new or there are new outpouchings(1,5).
  • Penetrating atherosclerotic ulcers: although less common in AAAs than in thoracic aortic aneurysms, they also indicates that an aneurysm is unstable. The expansion of such ulcers increases the risk of outpouching and rupture.

Communication

Abdominal aortic aneurysm rupture is a medical emergency associated with extremely high mortality and therefore requiring immediate surgical treatment. Referring doctor should be contacted.

References

CORREA, Ingrid Braga et al. Abdominal aortic aneurysms that have ruptured or are at imminent risk of rupture. Radiol Bras [online]. 2019, vol.52, n.3 [cited 2019-07-12], pp.182-186. Available from: <http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-39842019000300182&lng=en&nrm=iso>. Epub June 13, 2019. ISSN 0100-3984. http://dx.doi.org/10.1590/0100-3984.2017.0096.