Written by Clay Smith
Symptoms and signs of ruptured abdominal aortic aneurysm (rAAA) are frustratingly insensitive. CTA is essential and is accurate. POCUS can accurately tell you a AAA is present and hasten the tempo of the workup but is not meant to diagnose rupture.
Why does this matter?
Ruptured AAA is a can’t-miss diagnosis. The problem is, the presentation may be subtler than you might think. It could masquerade as a kidney stone or non-specific abdominal or back pain. Mortality is already 50-90%, and if we miss the diagnosis, this will almost certainly be fatal. How good are symptoms, signs, CTA, and ultrasound at helping us make the diagnosis?
You’d think you could tell when someone’s aorta explodes…
This was a systematic review and meta-analysis of 20 studies, 2,077 total patients. The gold standard was operative diagnosis of rAAA. Classic symptoms weren’t so classic after all. Sensitivity of abdominal pain was 62%, back pain 54%, and syncope 28%. For signs, hypotension was 31% sensitive, pulsatile abdominal mass 47%. CTA accuracy was lower than expected. Overall, sensitivity was 91.4%, specificity 93.6%. But all the included studies were as old as the hills (from 1984-1998). This accuracy just can’t be right for newer generation CTA. For diagnosing the presence of a AAA when rAAA was suspected, POCUS performed very well: sensitivity 97.8%, specificity 97.0%. Prevalence of indeterminate scans was largely not mentioned in most studies. Note, POCUS is not used to diagnose rupture, just presence of a AAA.
In summary, when you have a patient in whom rAAA is being considered in the differential diagnosis based on symptoms or signs, imaging is required. If there is any delay in obtaining CTA, grab the ultrasound and take a look. If you clearly don’t see a big aorta*, you can probably slow the tempo. But if you do, the pace needs to move even faster, and the patient needs to bump to the front of the CT queue or be transferred to a center with CTA and vascular surgery capabilities.
*Let’s define “big aorta” as >3cm at the infrarenal location. Please, if the ultrasound experts want to comment, that would be super helpful!
Accuracy of Presenting Symptoms, Physical Examination, and Imaging for Diagnosis of Ruptured Abdominal Aortic Aneurysm -Systematic Review and Meta-Analysis. Acad Emerg Med. 2022 Feb 27. doi: 10.1111/acem.14475. Online ahead of print.