Aneurysm, Abdominal Aortic (AAA), Imaging

Article Author:
Ryan Gibbons
Article Editor:
Michael Young
1/11/2019 12:28:11 PM
PubMed Link:
Aneurysm, Abdominal Aortic (AAA), Imaging


Abdominal Aortic Aneurysms (AAAs) are a relatively common pathology with a prevalence of 1.3% in patients over 50 years and an incidence in elderly men over 12%. Ruptured aneurysms have an exceptionally high mortality rate ranging 50% to 95%. In fact, mortality increases by 1% with each subsequent minute, mandating prompt diagnosis and intervention. Nearly 30% of ruptured AAAs are misdiagnosed on initial presentation, especially since physical exam has an exceedingly poor sensitivity less than 65%. Moreover, less than 25% of patients present with the characteristic triad of hypotension, abdominal pain, and a pulsatile abdominal mass.

Prompt diagnosis by utilizing point of care ultrasound has demonstrated sensitivities of 94% to 99%. Costantino et al. confirmed that bedside ultrasound is accurate within 4 millimeters of CT measurements with respect to AAA. Bedside ultrasound is a safe and effective diagnostic imaging modality, which can be performed in under 5 minutes. More significantly, its use has decreased mortality by 20% to 60%.


The retroperitoneal abdominal aorta enters the abdomen via the aortic hiatus caudal to the xiphoid process. It rests anterior to the vertebral body and parallel to the inferior vena cava.  Extending about 1 to 2 centimeters below the umbilicus, the aorta divides into the common iliac arteries at the level of L4. The aorta diminishes in size as it descends through the abdominal cavity, moving more superficially as well. As it moves caudally, the aorta has consecutive arterial branches: the celiac, superior mesenteric, renal then gonadal, and ultimately the inferior mesenteric. 

An aneurysm is classified as a focal dilatation greater than 50% of a vessel’s normal diameter. A diameter greater than 3 centimeters demarcates an AAA. Two categories of AAAs exist: fusiform and saccular. The majority are fusiform. Fusiform aneurysms expand circumferentially. Whereas saccular aneurysms are localized outpouchings, often secondary to an infectious etiology.

Approximately 90% of AAAs occur infrarenal, although the renal vessels are often difficult to image with a point of care ultrasound. Scan to where the aorta bifurcates to confirm visualization of the aorta in its entirety.


Who to Scan?

It is important to remember that less than 25% of individuals present with the classic triad of hypotension, abdominal pain, and a pulsatile abdominal mass.

Consider sonographic assessment of the abdominal aorta in the following instances:

  • Greater than 50 years old with one of the following: chest, abdominal, flank, groin, or back pain; renal colic; hematuria; or hydronephrosis 
  • Cardiac Arrest
  • Hypotension
  • Syncope
  • Thromboembolic events to the lower extremities
  • Neurologic deficit of the lower extremities

Expert consensus regarding sonographic screening for AAAs in asymptomatic individuals includes the following.

The United States Preventative Services Task Force (USPSTF) & the American Academy of Family Physicians (AAFP) recommendations:

  • Men greater than 65 years who ever smoked

Society for Vascular Surgery recommendations:

  • All men age greater than 65
  • Men greater than 55 with a family history of AAA
  • Women greater than 65 with family history of AAA or who have ever smoked

Risk Factors

  • Greater than 50 years old
  • Family history of AAA
  • Male
  • Hypertension
  • Smoking
  • Coronary artery disease
  • Diabetes mellitus
  • Hyperlipidemia
  • Peripheral arterial disease


There are no known contraindications for the sonographic assessment of the abdominal aorta.


Sonographic assessment of the aorta is performed in real time B-mode imaging programmed with the abdominal settings. The curvilinear transducer is ideal given its lower frequency and deeper penetration. However, the phased array transducer can be employed as well.


Similar to any sonographic examination, the appropriate configuration is necessary to acquire detailed images of the abdominal aorta. Place the patient in the supine position with the bed adjusted to the level of the provider’s waist. Darken the room and apply sufficient gel.

Initially, maximize the depth to visualize the most important landmark, the vertebral body. It should be hyperechoic with posterior shadowing. Once identified, adjust the depth accordingly to enhance your image.  Particularly, as you scan inferiorly towards the umbilicus, the aorta moves to a more superficial position, and less depth is needed.

Continuous, firm pressure will displace impeding bowel gas; and adjustments to the gain will reduce artifact. Modify the probe angle or move slightly off midline. Then angle or rock back medially to improve image acquisition. Or slide caudal to hindering bowel and then tilt cephalad to enhance sonographic visualization. The opposite technique works similarly.  Finally, turn the patient into the left lateral decubitus position. This may improve your images as well. Nevertheless, the aorta will not be visible in 5% of individuals. In these instances, advanced diagnostic imaging modalities, such as CT or MRA, will supplement the evaluation.


To begin, place the transducer below the xiphoid process in the transverse alignment. Perform a complete scan through the bifurcation of the aorta around the level of the umbilicus. Several consecutive videos may be necessary to image the entire aorta. Measure the abdominal aorta at its maximal diameter to include each outer wall. Dimensions are most precise with the probe positioned completely perpendicular to the aorta. Perform a similar scan in the sagittal view with the transducer position towards the patient’s head.

Be sure to include any visible thrombus. Thrombus will appear as an echogenic substance within the aorta. However, it is easily overlooked. Generally, it is best visualized along the anterolateral wall and may create a false lumen that underestimates the actual extent of an aortic aneurysm. 

In unstable patients, providers should routinely complete a right upper quadrant ultrasound to evaluate for pathologic fluid. The majority of AAAs rupture in the retroperitoneum (70% to 90%), where ultrasound cannot assess routinely. Nevertheless, one study established a sensitivity of 97% for identifying ruptured AAAs when the point of care ultrasound was combined with clinical gestalt.

Lastly, sonographic assessment of the aorta includes assessing for the occurrence of an intimal flap, the pathognomonic finding that is 100% specific for aortic dissections. Strict blood pressure management and emergent surgical consultation are mandated.


There are no known complications from the sonographic assessment of the abdominal aorta. Limitations include body habitus, bowel gas, and operator experience. Instead of a limited evaluation of the abdominal aorta, consider advanced imaging based on the patient's hemodynamic status.

Clinical Significance

More than 90% of abdominal aortic aneurysms occur below the renal arteries. By scanning to the level of the bifurcation, providers ensure complete visualization of the aorta.

Do not overlook an intraluminal thrombus. Include the thrombus to measure the diameter accurately.

Identify intimal flaps, which are pathognomonic for aortic dissections.

It can be difficult to differentiate the IVC from the aorta. Generally, the pulsatile aorta is thick walled, non-compressible, and positioned medial to the IVC. The IVC is thin-walled and compressible. It may appear to pulsate in lieu of its proximity to the aorta and secondary to the normal respiratory cycle. Use pulsed-wave Doppler to delineate the aorta’s pulsatile flow from the venous flow of the inferior vena cava, which should display mild respirophasic variation only.

Although the majority are retroperitoneal, when concerned for a ruptured AAA, perform a right upper quadrant ultrasound to assess for pathologic fluid.


Deaths: Final Data for 2011., Kochanek KD,Murphy SL,Xu J,, National vital statistics reports : from the Centers for Disease Control and Prevention, National Center for Health Statistics, National Vital Statistics System, 2015 Jul 27     [PubMed PMID: 26222597]
Prevalence and associations of abdominal aortic aneurysm detected through screening. Aneurysm Detection and Management (ADAM) Veterans Affairs Cooperative Study Group., Lederle FA,Johnson GR,Wilson SE,Chute EP,Littooy FN,Bandyk D,Krupski WC,Barone GW,Acher CW,Ballard DJ,, Annals of internal medicine, 1997 Mar 15     [PubMed PMID: 9072929]
Mortality from ruptured abdominal aortic aneurysm in Wales., Basnyat PS,Biffin AH,Moseley LG,Hedges AR,Lewis MH,, The British journal of surgery, 1999 Jun     [PubMed PMID: 10383576]
Accuracy of emergency medicine ultrasound in the evaluation of abdominal aortic aneurysm., Costantino TG,Bruno EC,Handly N,Dean AJ,, The Journal of emergency medicine, 2005 Nov     [PubMed PMID: 16243207]
Abdominal aortic aneurysm., Ernst CB,, The New England journal of medicine, 1993 Apr 22     [PubMed PMID: 8455684]
The rational clinical examination. Does this patient have abdominal aortic aneurysm? ., Lederle FA,Simel DL,, JAMA, 1999 Jan 6     [PubMed PMID: 9892455]
The accuracy of physical examination to detect abdominal aortic aneurysm., Fink HA,Lederle FA,Roth CS,Bowles CA,Nelson DB,Haas MA,, Archives of internal medicine, 2000 Mar 27     [PubMed PMID: 10737283]
The accuracy of physical examination to detect abdominal aortic aneurysm., Fink HA,Lederle FA,Roth CS,Bowles CA,Nelson DB,Haas MA,, Archives of internal medicine, 2000 Mar 27     [PubMed PMID: 10737283]
Ruptured abdominal aortic aneurysm: initial misdiagnosis and the effect on treatment., Akkersdijk GJ,van Bockel JH,, The European journal of surgery = Acta chirurgica, 1998 Jan     [PubMed PMID: 9537706]
The Impact of Initial Misdiagnosis of Ruptured Abdominal Aortic Aneurysms on Lead Times, Complication Rate, and Survival., Smidfelt K,Drott C,Törngren K,Nordanstig J,Herlitz J,Langenskiöld M,, European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery, 2017 May 16     [PubMed PMID: 28526396]
Misdiagnosis of ruptured abdominal aortic aneurysms., Marston WA,Ahlquist R,Johnson G Jr,Meyer AA,, Journal of vascular surgery, 1992 Jul     [PubMed PMID: 1619721]
Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm., Rubano E,Mehta N,Caputo W,Paladino L,Sinert R,, Academic emergency medicine : official journal of the Society for Academic Emergency Medicine, 2013 Feb     [PubMed PMID: 23406071]
The validity of ultrasonographic scanning as screening method for abdominal aortic aneurysm., Lindholt JS,Vammen S,Juul S,Henneberg EW,Fasting H,, European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery, 1999 Jun     [PubMed PMID: 10375481]
Operation for ruptured abdominal aortic aneurysms: a community-wide experience., Hoffman M,Avellone JC,Plecha FR,Rhodes RS,Donovan DL,Beven EG,DePalma RG,Frisch JA,, Surgery, 1982 May     [PubMed PMID: 7071748]
Suspected leaking abdominal aortic aneurysm: use of sonography in the emergency room., Shuman WP,Hastrup W Jr,Kohler TR,Nyberg DA,Wang KY,Vincent LM,Mack LA,, Radiology, 1988 Jul     [PubMed PMID: 3289085]
Screening for abdominal aortic aneurysm: a best-evidence systematic review for the U.S. Preventive Services Task Force., Fleming C,Whitlock EP,Beil TL,Lederle FA,, Annals of internal medicine, 2005 Feb 1     [PubMed PMID: 15684209]
Abdominal Aortic Aneurysm Screening: Do We Need to Shift Toward a Targeted Strategy?, Spanos K,Labropoulos N,Giannoukas A,, Angiology, 2017 Jan 1     [PubMed PMID: 28539057]
Update on Screening for Abdominal Aortic Aneurysm., Earnshaw JJ,Lees T,, European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery, 2017 May 16     [PubMed PMID: 28526395]
Screening for abdominal aortic aneurysm: a consensus statement., Kent KC,Zwolak RM,Jaff MR,Hollenbeck ST,Thompson RW,Schermerhorn ML,Sicard GA,Riles TS,Cronenwett JL,, Journal of vascular surgery, 2004 Jan     [PubMed PMID: 14718853]
Risk factors for abdominal aortic aneurysm: results of a case-control study., Blanchard JF,Armenian HK,Friesen PP,, American journal of epidemiology, 2000 Mar 15     [PubMed PMID: 10733039]
Screening for abdominal aortic aneurysm in asymptomatic adults., Ali MU,Fitzpatrick-Lewis D,Miller J,Warren R,Kenny M,Sherifali D,Raina P,, Journal of vascular surgery, 2016 Dec     [PubMed PMID: 27871502]
Screening results from a large United Kingdom abdominal aortic aneurysm screening center in the context of optimizing United Kingdom National Abdominal Aortic Aneurysm Screening Programme protocols., Benson RA,Poole R,Murray S,Moxey P,Loftus IM,, Journal of vascular surgery, 2016 Feb     [PubMed PMID: 26482996]
Prospective study of accuracy and outcome of emergency ultrasound for abdominal aortic aneurysm over two years., Tayal VS,Graf CD,Gibbs MA,, Academic emergency medicine : official journal of the Society for Academic Emergency Medicine, 2003 Aug     [PubMed PMID: 12896888]
Emergency department ultrasound scanning for abdominal aortic aneurysm: accessible, accurate, and advantageous., Kuhn M,Bonnin RL,Davey MJ,Rowland JL,Langlois SL,, Annals of emergency medicine, 2000 Sep     [PubMed PMID: 10969223]
The diagnosis of aortic dissection by emergency medicine ultrasound., Fojtik JP,Costantino TG,Dean AJ,, The Journal of emergency medicine, 2007 Feb     [PubMed PMID: 17307632]
Emergency ultrasound of the abdominal aorta by UK emergency physicians: a prospective cohort study., Dent B,Kendall RJ,Boyle AA,Atkinson PR,, Emergency medicine journal : EMJ, 2007 Aug     [PubMed PMID: 17652674]
Screening for abdominal aortic aneurysm in asymptomatic at-risk patients using emergency ultrasound., Moore CL,Holliday RS,Hwang JQ,Osborne MR,, The American journal of emergency medicine, 2008 Oct     [PubMed PMID: 18926345]