Abdominal aortic ultrasound

My DDU point form notes on abdominal aortic ultrasound and AAA…

The rest of my DDU notes are here.

Abdominal aorta and branches

Abdominal aortic aneurysm presentations

Suspect in > 60yo with any of

Presentations of AAA

pulsatile abdominal mass

pain: abdominal, chest, back, renal “colic”

hypotension, syncope

weakness, neurological changes in extremities

USS technique

Probe: ideally curvilinear – alternative phased array

Orientation: Marker cephalad in longitudinal and right in transverse (like FAST)

Position: supine ± knee bend (rarely lateral decubitus)

Start transversely in midline below xiphoid → see IVC anterior and lateral to vertebral column and aorta to left of IVC

Scan down to aortic bifurcation

Repeat in longitudinal

Longitudinal and transverse views of abdominal aorta from epigastrium to iliacs

impediments to scanning and tips

Bowel gas (in transverse colon + stomach):

Steady pressure → bowel undergoes peristalsis or is compressed

Jiggle → peristalsis, move bowel aside

Fan through windows between loops of bowel

Position in lateral decubitus

Obesity

Completely flat with hips and knees bent

Lower frequency

Surgical incisions, wounds, dressings

Pain

Look for

AAA

AAA scanning tips

Aortic dissection

Aortic dissection

IVC

normal is ≤ 2 cm

can be focally dilated near RA junction due to TR

pitfalls

mistaking IVC for aorta (both pulsatile)

small AAA (<4.5 cm) can rupture (just less common than larger AAA)

very sensitive for AAA cf insensitive for

• rupture (mainly retroperitoneal → USS doesn’t reliably see • intraperitoneal rupture with free fluid seen on USS, poor prognosis)
• dissection (floating intimal flap) – need to use CT or MRI to rule out if suspected (or if aortic root involved, TOE – suspect if pericardial effusion and AR)

Management algorithm for suspected AAA

Normal aorta → consider alternative Dx

AAA present, patient unstable or has acute symptoms due to AAA → vascular consult, prepare patient for surgery

in between (eg. incomplete exam, enlarged aorta, or normal exam but high suspicion) → CT ± vascular consult

Cover image: Normal abdominal aorta by James Heilman