Bedside aorta ultrasound reliably answers one question: is there an abdominal aortic aneurysm? In the unstable patient with abdominal, back, or flank pain, that answer changes the next ten minutes.
The exam is a continuous transverse sweep from the diaphragm to the bifurcation, measuring outer wall to outer wall. Partial visualization is an incomplete exam.
Curated from the POCUS 101 Aorta Ultrasound Made Easy: Step-By-Step Guide. The labeled images of landmarks and measurement technique are worth reviewing before your next scan.
Abdominal preset, depth ~15 cm to start. Phased array is an acceptable alternative.
Flexing the hips relaxes the abdominal wall. Steady, graded pressure displaces bowel gas — slow constant pressure works better than force.
The vertebral body's bright arc with clean shadowing is the deep landmark. The aorta sits just anterior and to the patient's left; the IVC lies to the right.
Transverse, just below the xiphoid · indicator to the patient's right
Identify the aorta anterior to the vertebral body: thick-walled, circular, and pulsatile. Confirm the celiac trunk branching (the "seagull sign") where it appears.
Sweep caudally · superior mesenteric artery level
Continue the transverse sweep. The superior mesenteric artery appears anterior to the aorta surrounded by a bright fat collar, with the splenic vein crossing above it. Measure here if the caliber looks abnormal.
Sweep to the umbilicus · follow through the iliac bifurcation
Most AAAs are infrarenal, so the distal aorta is the highest-yield segment. Follow the aorta through its bifurcation into the common iliac arteries and assess their caliber.
Transverse plane · outer wall to outer wall · widest visible diameter
Measure the maximal anterior-posterior diameter from outer wall to outer wall, perpendicular to the vessel. Include mural thrombus in the measurement — measuring only the flow lumen underestimates the true diameter.
A long-axis view can supplement, but be aware of the cylinder-tangent effect: an off-center longitudinal slice falsely narrows the vessel.
| Measurement | Threshold | Means |
|---|---|---|
| Normal aorta | < 3 cm | Tapers distally; no aneurysm |
| AAA | ≥ 3 cm | Aneurysm; asymptomatic findings need arranged follow-up and surveillance |
| Large AAA | > 5 cm | Elevated rupture risk; expedited vascular surgery involvement |
| Symptomatic AAA | any size + symptoms | Treated as rupture until proven otherwise — emergent vascular consultation |
| Common iliac artery | > 1.5 cm | Iliac aneurysm |
| Intimal flap (if seen) | mobile linear echo within the lumen | Suggests dissection; confirm with CT angiography |
An unstable patient with a visualized AAA and a compatible clinical picture goes to vascular surgery on the ultrasound finding — not after a confirmatory CT.
Mural thrombus lines many aneurysms and can make a 6 cm AAA look like a 3 cm lumen. Measure outer wall to outer wall, always including thrombus.
Retroperitoneal blood is largely invisible to bedside ultrasound. The absence of free fluid provides no reassurance in a symptomatic patient with an AAA.
The infrarenal segment is where most aneurysms live. Ending the sweep at the umbilicus without reaching the bifurcation leaves the highest-yield segment unexamined.
The IVC mimics the aorta in poor windows. Check position relative to the vertebra, wall thickness, compressibility, and respiratory variation before believing a measurement.
Bowel gas is displaced by steady, graded probe pressure held over seconds. Repositioning the patient or jiggling the probe gently also helps clear the window.
A ruptured or expanding AAA presenting as first-time "renal colic" is a well-documented fatal miss. The aorta sweep adds two minutes to the renal scan — pair it with Renal (No. 010).
A starting template for the POCUS note. Text in brackets [ ] and pick-lists in { } are fields to complete. Save it as a SmartPhrase, then edit every field to match the actual study.
POINT-OF-CARE ULTRASOUND: ABDOMINAL AORTA
Indication: {abdominal / back pain : ? AAA : hypotension : syncope} [***]
Exam type: Focused / limited, transverse sweep
Operator: @ME@ Interpretation: independent, real-time
Probe: curvilinear
FINDINGS (outer wall to outer wall, transverse)
- Proximal aorta: *** cm
- Mid aorta: *** cm
- Distal aorta: *** cm
- Iliac vessels: {normal : aneurysmal ***}
- Intraluminal thrombus: {none : present}
- Intimal flap: {none seen : seen - dissection possible, CTA advised}
IMAGE QUALITY: adequate / limited by [***] (bowel gas / habitus)
Images saved and archived to [PACS / Qpath / ***].
IMPRESSION: {aorta <3 cm, no aneurysm : AAA measuring *** cm : ***}.
US does not reliably exclude rupture; symptomatic AAA treated as rupture
until proven otherwise.
I personally performed and interpreted this study.
Electronically signed: @ME@ @TD@ @NOW@
Sample template only — not a validated institutional SmartPhrase. Verify wording, image-archival, and attestation requirements against your department's POCUS credentialing, coding, and compliance policies before clinical use. Documentation supports, but does not replace, the medical record and QA workflow.