Written by: John Li, MD (NUEM ‘24) Edited by: Andra Farcas, MD (NUEM ‘21) Expert Commentary by: John Bailitz, MD & Shawn Luo, MD (NUEM ‘22)
SonoPro Tips and Tricks
Welcome to the NUEM Sono Pro Tips and Tricks Series where Sono Experts team up to take you scanning from good to great for a problem or procedure! For those new to the probe, we recommend first reviewing the basics in the incredible FOAMed Introduction to Bedside Ultrasound Book and 5 Minute Sono. Once you’ve got the basics beat, then read on to learn how to start scanning like a Pro!
Aortic ultrasound is a staple in emergency point of care ultrasound. It has incredible sensitivity (97.5-100%) and specificity (94.1-100%) in detecting abdominal aortic aneurysms and can provide a diagnosis for critically ill patients in seconds. [1-4] However, it can often be a technically difficult study for beginner sonographers due to shadowing bowel gas and patient body habitus. Follow along in this installment of our Sono Pro Tips and Tricks Series to become an expert in finding aortas!
Beyond the classic elderly male smoker with abdominal, flank, or back pain, what are other scenarios where you would use aortic ultrasound?
Older patients with limb ischemia - an aortic aneurysm can have atherosclerosis or a mural thrombus which can embolize and cause an arterial occlusion!
“But they fixed my aorta!” Aortic endograft leakage can sometimes present with symptoms that are similar to a AAA rupture, such as back pain, flank pain, or hemodynamic instability.
How to scan like a Pro
Always Start Smart: Aortic ultrasound can be tricky because of factors that seem out of our control, such as bowel gas or patient body habitus.
When scanning for an abdominal aortic aneurysm, start scanning in the epigastric region with a transverse view and apply constant pressure, gently pushing the bowel gas out of the way as you slide the probe down towards the patient’s feet.
Tell your patients to bend their knees! This relaxes the abdominal musculature and can help you move bowel gas or make better contact with the probe.
What if you still can’t see it? Try looking in the right upper quadrant view of the FAST exam!
Start with your probe in the right mix-axillary line and use the liver as your acoustic window. You may need to fan anteriorly or posteriorly depending on the patient’s body habitus and your positioning.
Unfortunately, this view predominantly visualizes the superior aspect of the abdominal aorta, and it can be difficult to visualize the inferior abdominal aorta or the bifurcation.
Here we are looking at a modified RUQ view, where the aorta is visualized on the bottom part of the screen using the liver as an acoustic window. (acep.org)
Pro Pickups!
What’s that weird aneurysm?
Most people are familiar with the classic fusiform aortic aneurysm, but saccular aneurysms can be easily missed because of shadowing bowel gas obstructing parts of the aorta. Saccular aneurysms actually have a higher risk of rupture and repair is recommended for smaller diameters.
Here you can see two images in the longitudinal axis of the different kinds of abdominal aortic aneurysms. On the left is a saccular aneurysm and on the right is a fusiform one. Be sure to pay attention to the mural thrombus in the walls of both of these aortas - they can embolize and cause arterial occlusions! (med.emory.edu)
2. How big is that aorta anyways?
Be sure to always measure the aorta from outside wall to outside wall!
Many aortic aneurysms have a mural thrombus or intraluminal clot, and it can be very easy to mistake these for extra-luminal contents.
Remember the concerning numbers: >5.5cm for men and >5cm for women!
What the Pros Do Next
Abdominal Aortic Aneurysm
If the patient is hemodynamically unstable (defined as BP <90/60, altered mental status, or other signs of end-organ damage), go straight to the OR!
If the patient is hemodynamically stable (defined as the absence of any of the above), then the next step is to obtain further imaging, such as a CT Angiogram, which is the imaging gold standard.
If you are concerned about a large AAA that could be a contained leak but the patient is hemodynamically stable, then we recommend an emergent vascular surgery consult
If you find a small AAA (defined as <5cm in women or <5.5cm in men) that you do not think is actively contributing to the patient’s symptoms, then we recommend outpatient vascular surgery follow up
SonoPro Tips - Where to Learn More
Do you want to review more examples of pathologic images that you may see when you are doing an aortic ultrasound? Be sure to check out The Pocus Atlas by our expert editor Dr. Macias. Aortic pathology is quite rare, and going through these images will help immensely in recognizing this diagnosis in emergent situations. If you’re interested in looking at some of the evidence behind aortic ultrasound, be sure to check out the evidence atlas here as well.
References
Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med. 2013 Feb;20(2):128-38. doi: 10.1111/acem.12080. PMID: 23406071.
Hunter-Behrend, Michelle, and Laleh Gharahbaghian. “American College of Emergency Physicians.” ACEP // Home Page, 2016, www.acep.org/how-we-serve/sections/emergency-ultrasound/news/february-2016/tips-and-tricks-big-red---the-aorta-and-how-to-improve-your-image/.
Ma, John, et al. Ma and Mateer's Emergency Ultrasound. McGraw-Hill Education, 2020.
Mallin, Mike, and Matthew Dawson. Introduction to Bedside Ultrasound: Volume 1. Emergency Ultrasound Solutions, 2013.
Macias, Michael. TPA, www.thepocusatlas.com/.
Expert Commentary
Another great Sono Pro Post! Thank you John Li and Andra for helping everyone move from good to great when scanning for Abdominal Aortic Aneurysms. As noted, this application defines Emergency Ultrasound as a fast (pun intended), accurate, and life saving diagnostic tool for every EM physicians tool belt. When consistent probe pressure does not do the trick, consider the RUQ view for a quick look. Since most AAA’s are fusiform, this may quickly confirm your suspicions and prompt the call to get the OR ready. Be sure to visualize the entire abdominal aorta throughout in both short and long axis to identify saccular aneurysms and even the rare aortic occlusion!
John Bailitz, MD
Vice Chair for Academics, Department of Emergency Medicine
Professor of Emergency Medicine, Feinberg School of Medicine
Northwestern Memorial Hospital
Shawn Luo, MD
PGY4 Resident Physician
Northwestern University Emergency Medicine
How To Cite This Post:
[Peer-Reviewed, Web Publication] Li, J. Farcas, A. (2021 Oct 11). SonoPro Tips and Tricks for Aortic Aneurysm. [NUEM Blog. Expert Commentary by Bailitz, J. Shawn, L.]. Retrieved from http://www.nuemblog.com/blog/sonopro-tips-and-tricks-for-aortic-aneurysm
