Type:
Educational Exhibit
Keywords:
Aneurysms, Acute, Diagnostic procedure, CT-Angiography, CT, Arteries / Aorta, Abdomen
Authors:
R. M. Antunes, P. G. M. G. Ferreira; Lisbon/PT
DOI:
10.1594/ecr2018/C-2943
Background
An abdominal aortic aneurysm (AAA) is a focal dilatation of the aorta measuring at least 3 cm in maximal diameter or ≥1.5 times the normal proximal diameter.
The great majority are true aneurysms (focal bulging that includes all layers of the aortic wall).
Pseudoaneurysms or false aneurysms are only contained by the outermost layer,
the adventicia,
and although are more commonly associated with rupture,
they are rarer and usually occur in the setting of trauma.
AAA can also be classified based on morphology as either fusiform or saccular; their relationship to the renal arteries – suprarenal,
juxtarenal or infrarenal; and their aetiology – degenerative,
inflammatory or mycotic [1,
2].
Rupture is the most dreadful complication of an AAA and carries an elevated mortality rate.
The risk of rupture increases with the diameter of the aneurysm,
becoming significant with diameters >5.5cm.
A recent study suggested the risk of rupture per year to be 5.3% for AAA between 5.5 and 6 cm,
4.1% per year for AAA 6.1 to 7 cm and 6.3% per year for AAA > 7 cm [3].
Other risk factors associated with rupture include female gender,
cigarette smoking,
low forced expiratory volume in 1 second,
elevated mean blood pressure and treatment with immunomodulatory drugs [4].
When there’s high clinical suspicion of a rupture AAA,
imaging is not necessary and should even be avoided since time is crucial [4].
When used,
computed tomography (CT) is the modality of choice and although the imaging findings of frank rupture are readily recognizable,
the signs of impending rupture can be subtler [2,
4].
Knowledge of the various imaging scenarios is of utmost importance for the appropriate management of the patient.