• Abdominal aortic aneurysms are typically asymptomatic and will progressively expand until they rupture. Ruptured aortic aneurysms have a mortality rate of 85-90% (Kent 2014).
  • Prevalence rates are estimated to be 1.3-8.9% in men and 1.0-2.2% in women with main  risk factors of smoking, age, family history, and hypertension (Sakalihasan 2005).


  • In the primary care setting, the US Preventive Services Task Force recommends screening for abdominal aortic aneurysms (AAA) in men 65-75 years old who have ever smoked (grade B). 
  • In the ED, AAA should be on the differential in the setting of pain, hypotension and a pulsatile mass. AAA should also be considered in at-risk patients who present with syncope or signs of retroperitoneal hemorrhage. 
  • Emergency ultrasound of the abdominal aorta by emergency medicine physicians has been shown to be sensitive and specific. One prospective study in 2008 found bedside ultrasound to be 100% sensitive and 98% specific in detecting a AAA (Tayal 2008).


  • The low-frequency, 3.5 MHz curvilinear probe is typically used for imaging of the aorta (Dean 2008).
  • Beginning in the epigastric area, with the probe in the transverse plane, identify the vertebral body. The aorta should be visualized above the vertebral body on patient’s left.
  • Short axis images should be obtained of the patient’s proximal abdominal aorta as well as the distal abdominal aorta, just above the site of the bifurcation into the iliac arteries. 
  • A long axis view should be obtained with the probe in the sagittal plane. 
  • A short axis view of the iliacs should be obtained distal to the bifurcation.
  • Use the measurement calipers to measure the anterior-to-posterior diameter of the abdominal aorta using the outer walls.

Short axis. “Ultrasound Assessment of Abdominal Aortic Aneurysms.” Medscape,

Long axis.  “POCUS Exams – Aorta.” Ultrasound Idiots,


  • An abdominal aortic aneurysm is diagnosed when the diameter is greater than 3.0 cm.
  • The aorta should taper as the vessel is traced distally. An aorta that dilates should prompt further evaluation, even if the measurements remain within normal limits.
  • Complete evaluation should trace past the bifurcation and include measurements of the common iliac vessels. These should measure <1.5 cm in women and <1.8 cm in adult men.

8x8cm AAA including thrombus.  Bookatz, Allen, et al. “Aortic Ultrasound.” WikEM, 30 Dec. 2017,

Measure from outer edge to outer edge.  “Ultrasound Assessment of Abdominal Aortic Aneurysms.” Medscape,

Common Pitfalls

  • Bowel gas will occasionally obscure the image. If this occurs, place additional pressure on the probe and gently fan up and down in an attempt to displace the bowel gas.
  • Accurate measurements require measurement from the outer wall to the outer wall. Take care not to confuse the inner edge of a thrombus with the outer wall of the abdominal aorta.
  • Be sure to not confuse the IVC with the abdominal aorta. The IVC is on the patient’s right and is typically non-pulsatile and compressible. Additionally, doppler mode can help to identify pulsatile waveforms consistent with aortic blood flow.

Take Home Points

  • Consider AAA in setting of pain, hypotension, pulsatile mass, or syncope, especially in older men with a smoking history
  • AAA is diagnosed when the outer wall to outer wall measurement exceeds 3.0 cm. Be careful not to mistake the inner rim of a thrombus for the outer wall of the abdominal aorta. 
  • Take the time necessary to differentiate the abdominal aorta from the IVC. If bowel gas is obscuring the image, apply increased pressure and slowly fan up and down.