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Abdominal Aortic Aneurysm (AAA)

General Information


  • abnormal irreversible full-thickness dilation of abdominal aorta resulting in diameter ≥ 3 cm or exceeding normal vessel diameter by > 50%1,4 )4
  • definition of aortic diameter ≥ 3 cm may not be appropriate for women who have smaller diameter arteries than men or for patients with arteriomegaly1
  • aneurysms may be classified as small or large
    • small aneurysm typically defined as aortic diameter < 5.5 cm, but may sometimes be defined as 3-4.9 cm (30-49 mm) or 3-5.5 cm (30-55 mm)1,3
    • large aneurysm typically defined as ≥ 5.5 cm (55 mm)1

Also called

  • atherosclerotic aortic aneurysm
  • aortic aneurysm


  • normal adult abdominal aortic diameters
    • varies based on age, sex, body size, and blood pressure3
    • infrarenal aortic diameter of 2.7 cm (27 mm) represents 95th percentile for men aged 65-83 years2
    • normal aortic diameters slightly smaller in women than men, but differences in diameter not great enough to influence definition of abdominal aneurysm2
    • normal abdominal aorta diameters based on sex2
       Supraceliac Abdominal Aorta Suprarenal Abdominal Aorta Infrarenal Abdominal Aorta Infrarenal Abdominal Aorta
      Measurement methodComputed tomographyComputed tomographyComputed tomography, IV arteriographyB-mode ultrasound, computed tomography, IV arteriography
      Female mean diameter2.1-2.31 cm (21-23.1 mm)1.86-1.88 cm (18.6-18.8 mm)1.66-2.16 cm (16.6-21.6 mm)1.19-1.87 cm (11.9-18.7 mm)
      Female standard deviation0.27 cm (27 mm)0.09-0.21 cm (0.9-2.1 mm)0.22-0.32 cm (2.2-3.2 mm)0.09-0.34 cm (0.9-3.4 mm)
      Male mean diameter2.5-2.72 cm (25-27.2 mm)1.98-2.27 cm (19.8-22.7 mm)1.99-2.39 cm (19.9-23.9 mm)1.41-2.05 cm (14.1-20.5 mm)
      Male standard deviation0.24-0.35 cm (24-35 mm)0.19-0.23 cm (1.9-2.3 mm)0.3-0.39 cm (3-3.9 mm)0.04-0.37 cm (0.4-3.7 mm)
  • true aneurysm defined as dilation of artery that involves all 3 layers of artery wall (intima, media, and adventitia)1
  • false aneurysm (also called pseudoaneurysm)1
    • defined as dilation secondary to arterial injury and without dilation of all 3 layers but with outer wall lacking organized vascular structure
    • may also occur due to infiltration of blood through dissection at level of medial layer
  • ectatic aorta (also called aortic ectasia or subaneurysmal aorta) defined as abdominal aortic diameter of 2.5-2.9 cm (mnh25884861pcxh101987981pmdc25884861pAm Fam Physician 2015 Apr 15;91(8):538full-text)


  • type by location of aneurysm4
    • infrarenal (most common) occurs below the renal arteries
    • suprarenal occurs above the renal arteries and involves origin of ≥ 1 visceral arteries
    • pararenal involves origins of renal arteries
    • juxtarenal involves origin distal (but very close to) renal arteries2
  • type by morphology1
    • fusiform (most common) - dilation involves whole circumference of artery
    • saccular - dilation only parts of circumference
  • "atherosclerotic" or nonspecific aneurysm is most common type and may be related to overproduction of proteases such as matrix metalloproteinase MMP-22
  • congenital aneurysm1,2
    • abdominal aortic aneurysm (AAA) may be more frequent in individuals with genetic predisposition to connective tissue disorders
    • syndromes with genetic predisposition to AAA
  • false aneurysms may be secondary to arterial injury such as inflammatory aneurysm or infectious ("mycotic") aneurysm


General references used

  1. Sakalihasan N, Michel JB, Katsargyris A, Kuivaniemi H, Defraigne JO, Nchimi A, Powell JT, Yoshimura K, Hultgren R. Abdominal aortic aneurysms. Nat Rev Dis Primers. 2018 Oct 18;4(1):34
  2. Hirsch AT, Haskal ZJ, Hertzer NR, et al; ACC/AHA 2005 Practice Guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): a collaborative report from the American Association 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): endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation; National Heart, Lung, and Blood Institute; Society for Vascular Nursing; TransAtlantic Inter-Society Consensus; and Vascular Disease Foundation. Circulation. 2006 Mar 21;113(11):e463-654PDF
  3. Erbel R, Aboyans V, Boileau C, et al. ESC Committee for Practice Guidelines. 2014 ESC Guidelines on the diagnosis and treatment of aortic diseases: Document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult. The Task Force for the Diagnosis and Treatment of Aortic Diseases of the European Society of Cardiology (ESC). Eur Heart J. 2014 Nov 1;35(41):2873-926full-text
  4. Kent KC. Clinical practice. Abdominal aortic aneurysms. N Engl J Med. 2014 Nov 27;371(22):2101-8
  5. Chaikof EL, Dalman RL, Eskandari MK, Jackson BM, Lee WA, Mansour MA, Mastracci TM, Mell M, Murad MH, Nguyen LL, Oderich GS, Patel MS, Schermerhorn ML, Starnes BW. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018 Jan;67(1):2-77.e2

Recommendation grading systems used

  • American College of Cardiology Foundation/American Heart Association (ACCF/AHA) grading system for recommendations
    • classifications of recommendations
      • Class I - procedure or treatment should be performed or administered
      • Class IIa - reasonable to perform procedure or administer treatment, but additional studies with focused objectives needed
      • Class IIb - procedure or treatment may be considered; additional studies with broad objectives needed, additional registry data would be useful
      • Class III - procedure or treatment should not be performed or administered because it is not helpful or may be harmful
        • Class III ratings may be subclassified as Class III No Benefit or Class III Harm
    • levels of evidence
      • Level A - data derived from multiple randomized clinical trials or meta-analyses
      • Level B - data derived from single randomized trial or nonrandomized studies
      • Level C - only expert opinion, case studies, or standard of care
  • United States Preventive Services Task Force (USPSTF) grades of recommendation (prior to May 2007)
    • Grade A - USPSTF strongly recommends that clinicians provide the service to eligible patients, based on good evidence that the service improves important health outcomes and that benefits substantially outweigh harms
    • Grade B - USPSTF recommends that clinicians provide the service to eligible patients, based on at least fair evidence that the service improves important health outcomes and that benefits outweigh harms
    • Grade C - USPSTF makes no recommendation for or against routinely providing the service, based on at least fair evidence that the service can improve health outcomes but the balance of benefits and harms is too close to justify a general recommendation
    • Grade D - USPSTF recommends against routinely providing the service to asymptomatic patients, based on at least fair evidence that the service is ineffective or that harms outweigh benefits
    • Grade I - USPSTF concludes that the evidence is insufficient to recommend for or against routinely providing the service
    • Reference - USPSTF Grade Definitions
  • European Society of Cardiology (ESC) grading system for recommendations
    • classes of recommendations
      • Class I - evidence and/or general agreement that given treatment or procedure is beneficial, useful, and effective
      • Class II - conflicting evidence and/or divergence of opinion about usefulness/efficacy of given treatment or procedure
        • Class IIa - weight of evidence/opinion in favor of usefulness/efficacy
        • Class IIb - usefulness/efficacy less well established by evidence/opinion
      • Class III - evidence or general agreement that given treatment or procedure is not useful/effective, and in some cases may be harmful
    • levels of evidence
      • Level A - data derived from multiple randomized clinical trials or meta-analyses
      • Level B - data derived from single randomized trial or large nonrandomized studies
      • Level C - consensus of opinion of experts and/or small studies, retrospective studies, registries
    • Reference - ESC guideline on diagnosis and treatment of aortic diseases: document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult (25173340Eur Heart J 2014 Nov 1;35(41):2873)
  • Society for Vascular Surgery (SVS) grading system for recommendations
    • strength of recommendation
      • GRADE 1 - strong recommendation; high confidence that benefit clearly outweighs risk
      • GRADE 2 - weak recommendation; benefit and risk closely balanced
    • levels of evidence
      • Level A - high-quality evidence; further study unlikely to change conclusions
      • Level B - moderate-quality evidence; further study likely to affect conclusions
      • Level C - low-quality evidence; further study very likely to change conclusions

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Special acknowledgements

  • The American College of Physicians (Marjorie Lazoff, MD, FACP; ACP Deputy Editor, Clinical Decision Resource) provided review in a collaborative effort to ensure DynaMed provides the most valid and clinically relevant information in internal medicine.
Choosing Wisely Canada acknowledges dissemination of their recommendations through DynaMed Plus to reach the point of clinical decision-making.
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National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T114361, Abdominal Aortic Aneurysm (AAA); [updated 2018 Nov 30, cited place cited date here]. Available from Registration and login required.

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