CT of abdominal aortic aneurysm

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Authors: Rodrigo Horstmann Castilhos; Mikael Häggström [notes 1]
Because it is a widely available, rapid imaging method, computed tomography (CT) angiography is the exam of choice in such cases.[1]

Planning

Choice of modality

Evaluation

Size classification

Size classification of infrarenal aorta edit
Ectatic or
mild dilatation
>2.0 cm and <3.0 cm[2]
Moderate 3.0 - 5.0[2] (or 5.5)[3] cm
Large or severe >5.0[2] or 5.5[3] cm


Abdominal aortic aneurysms are commonly divided according to their size and symptomatology. An aneurysm is usually defined as an outer aortic diameter over 3 cm (normal diameter of the aorta is around 2 cm),[4] or more than 50% of normal diameter.[5] The suprarenal aorta normally measures about 0.5 cm larger than the infrarenal aorta.[6]

Signs of 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.[1]
  • 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.[1]

Signs of 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.[1]
  • 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.[1]
  • 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]
  • 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.[1]

Reporting

See also: General notes on reporting

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.[1]

See also

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Corrêa, Ingrid Braga; Alves, Bruna Leal Torres; Oliveira Sobrinho, Tarcísio Angelo de; Ramos, Laura Filgueiras Mourão; Diniz, Renata Lopes Furletti Caldeira; Ribeiro, Marcelo Almeida (2019). "Abdominal aortic aneurysms that have ruptured or are at imminent risk of rupture ". Radiologia Brasileira 52 (3): 182–186. doi:10.1590/0100-3984.2017.0096. ISSN 1678-7099. 
  2. 2.0 2.1 2.2 . Archived copy. Archived from the original on 2017-09-08. Retrieved on 2017-08-23. Page 56] in: Philip Lumb (2014). Critical Care Ultrasound E-Book . Elsevier Health Sciences. ISBN 9780323278171. 
  3. 3.0 3.1 "Screening for abdominal aortic aneurysms: single centre randomised controlled trial ". BMJ 330 (7494): 750. Apr 2005. doi:10.1136/bmj.38369.620162.82. PMID 15757960. 
  4. "ACC/AHA Guidelines for the Management of Patients with Peripheral Arterial Disease (lower extremity, renal, mesenteric, and abdominal aortic): a collaborative report from the American Associations for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (writing committee to develop guidelines for the management of patients with peripheral arterial disease)—summary of recommendations ". J Vasc Interv Radiol 17 (9): 1383–97; quiz 1398. September 2006. doi:10.1097/01.RVI.0000240426.53079.46. PMID 16990459. 
  5. Solomon, Caren G.; Kent, K. Craig (2014). "Abdominal Aortic Aneurysms ". New England Journal of Medicine 371 (22): 2101–2108. doi:10.1056/NEJMcp1401430. ISSN 0028-4793. PMID 25427112. 
  6. Jeffrey Jim, Robert W Thompson (2018-03-05). Clinical features and diagnosis of abdominal aortic aneurysm. UpToDate. Archived from the original on 2018-03-30.