Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta that are 50% greater than the proximal normal segment or that are >3 cm in maximum diameter.
Its prevalence increases with age. Males are much more commonly affected than females (with a male:female ratio of 4:1).
It is the tenth most common cause death in the Western world. Approximately 10% of persons older than 65 years have an AAA.
Most AAAs are asymptomatic unless they leak or rupture. Unruptured aneurysms may uncommonly cause abdominal or back pain, or a pulsatile mass, if large.
Ruptured aneurysms present with severe abdominal or back pain, hypotension and shock. The mortality rate from a ruptured AAA is high (59-83% of patients succumb to death before they make it to a hospital or undergo surgery). The operative mortality rate for those who make it to surgery tends to be around 40%. Elective surgery mortality is much lower (4-6%).
- atherosclerosis (most common)
- inflammatory abdominal aortic aneurysm
- chronic aortic dissection
- vasculitis, e.g. Takayasu arteritis
- connective tissue disorders, e.g.
- mycotic aneurysm
- traumatic pseudoaneurysm
- anastomotic pseudoaneurysm
common iliac artery (CIA) aneurysm
- AAA commonly extends into common iliac arteries
- vast majority of patients with CIA aneurysms have an AAA
- isolated CIA aneurysms are rare
popliteal artery aneurysm
- 10-14% of patients with AAA have popliteal artery aneurysm
- 30-50% of patients with popliteal artery aneurysm have an AAA
Role of imaging
- detection of AAA
- monitoring of the rate of growth
- pre-operative planning
- post-operative follow-up
An aneurysm may be visible as an area of curvilinear calcification in the paravertebral region on either abdominal or lumbar spine films performed for alternative indications. Radiographs are not optimal for detection or follow-up.
Ultrasound assessment is simple, safe and inexpensive. It has a reported sensitivity of 95% and specificity close to 100%. It is usually the preferred choice for monitoring of small aneurysms. The measurement of error of ultrasound evaluation of AAAs is 4 mm 12, but remember that it will never decrease in size.
This is considered the imaging gold standard but has a high radiation dose. Excellent for pre-operative planning as it accurately delineates the size and shape of the AAA and its relationship to branch arteries and the aortic bifurcation. It is also superior to ultrasound in detecting and sizing common iliac artery aneurysms.
Signs of rupture or impending rupture include:
- draped aorta sign: sign of contained rupture
- high-attenuation crescent sign: sign of impending rupture
- retroperitoneal haematoma
Same as for CTA but can be more costly and less widely available.
Does not show true aneurysm size if there is mural thrombus but good at delineating branch vessels. Usually performed intraoperatively during treatment.
Reported complications include:
- pseudoaneurysm from chronic contained leak/rupture
- distal thromboembolism
- thrombotic occlusion of a branch vessel
- compression of adjacent structures if large (rare)
- vertebral erosion
Treatment and prognosis
The natural history of abdominal aortic aneurysms is that of slow expansion and rupture with devastating consequences.
The risk of rupture is proportional to the size of the aneurysm and the rate of growth. Differing rates of rupture for a given aneurysm size have been reported in the literature but the general consensus is that aneurysms greater than 5.0 cm in women and 5.5 to 6.0 cm in men carry a significantly increased risk of rupture and should be treated. Furthermore, aneurysms that expand greater than 10 mm per year are also at significant risk of rupture and are considered for treatment even when less than 5.0 cm.
Follow up intervals for imaging an enlarged infrarenal abdominal aorta (when initially detected) 11:
- <2.5 cm: follow up not needed
- 2.5-2.9 cm: 5 year interval
- 3.0-3.4 cm: 3 year interval
- 3.5-3.9 cm: 2 year interval
- 4.0-4.4 cm: 1 year interval
- 4.5-4.9 cm: 6 month interval
- 5.0-5.5 cm: 3-6 month interval
- >5.5 cm: treatment
Management options include:
- endovascular aneurysm repair (EVAR)
- open surgical repair
Treatment is recommended in surgically fit patients if the aneurysm is greater than 5.0 cm diameter in women and 5.5 cm diameter in men. Treatment is also considered if aneurysm growth rate exceeds 10 mm per year in smaller aneurysms.
- acute aortic syndrome
- thoracic aortic aneurysm
- abdominal aortic aneurysm
- endovascular aneurysm repair (EVAR)
- reporting tips for aortic aneurysms
- traumatic aortic injuries
- 1. Pande RL, Beckman JA. Abdominal aortic aneurysm: populations at risk and how to screen. J Vasc Interv Radiol. 2008;19 (6 Suppl): S2-8. doi:10.1016/j.jvir.2008.03.010 - Pubmed citation
- 2. Brown PM, Zelt DT, Sobolev B. The risk of rupture in untreated aneurysms: the impact of size, gender, and expansion rate. J. Vasc. Surg. 2003;37 (2): 280-4. doi:10.1067/mva.2003.119 - Pubmed citation
- 3. Kaufman JA, Lee MJ. Vascular and interventional radiology, the requisites. Mosby Inc. (2004) ISBN:0815143699. Read it at Google Books - Find it at Amazon
- 4. Wright LB, Matchett WJ, Cruz CP et-al. Popliteal artery disease: diagnosis and treatment. Radiographics. 24 (2): 467-79. doi:10.1148/rg.242035117 - Pubmed citation
- 5. Rakita D, Newatia A, Hines JJ et-al. Spectrum of CT findings in rupture and impending rupture of abdominal aortic aneurysms. Radiographics. 27 (2): 497-507. doi:10.1148/rg.272065026 - Pubmed citation
- 6. Siegel CL, Cohan RH, Korobkin M et-al. Abdominal aortic aneurysm morphology: CT features in patients with ruptured and nonruptured aneurysms. AJR Am J Roentgenol. 1994;163 (5): 1123-9. AJR Am J Roentgenol (citation) - Pubmed citation
- 7. Schwartz SA, Taljanovic MS, Smyth S et-al. CT findings of rupture, impending rupture, and contained rupture of abdominal aortic aneurysms. AJR Am J Roentgenol. 2007;188 (1): W57-62. doi:10.2214/AJR.05.1554 - Pubmed citation
- 8. Roy J, Labruto F, Beckman MO et-al. Bleeding into the intraluminal thrombus in abdominal aortic aneurysms is associated with rupture. J. Vasc. Surg. 2008;48 (5): 1108-13. doi:10.1016/j.jvs.2008.06.063 - Pubmed citation
- 9. Apter S, Rimon U, Konen E et-al. Sealed rupture of abdominal aortic aneurysms: CT features in 6 patients and a review of the literature. Abdom Imaging. 2010;35 (1): 99-105. doi:10.1007/s00261-008-9488-1 - Pubmed citation
- 10. Lai CC, Tan CK, Chu TW et-al. Chronic contained rupture of an abdominal aortic aneurysm with vertebral erosion. CMAJ. 2008;178 (8): 995-6. CMAJ (full text) - doi:10.1503/cmaj.070332 - Free text at pubmed - Pubmed citation
- 11. Khosa F, Krinsky G, Macari M et-al. Managing incidental findings on abdominal and pelvic CT and MRI, Part 2: white paper of the ACR Incidental Findings Committee II on vascular findings. J Am Coll Radiol. 2013;10 (10): 789-94. doi:10.1016/j.jacr.2013.05.021 - Pubmed citation
- 12. Singh K, Bønaa KH, Solberg S et-al. Intra- and interobserver variability in ultrasound measurements of abdominal aortic diameter. The Tromsø Study. Eur J Vasc Endovasc Surg. 1998;15 (6): 497-504. Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Abdominal aortic aneurysm (AAA)||✗|
|Abdominal aortic aneurysms||✗|
|Abdominal aortic aneurysmal dilatation||✗|