AORTA By Dr. Robert Hyde University of Pittsburgh Medical Center INDICATIONS: • • • •
Pain in the back, abdomen, flank or groin Syncope or dizziness Unexplained hypotension Palpable abdominal mass KEY QUESTION:
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Is the abdominal aorta enlarged? TECHNIQUE:
A low frequency transducer (2-5 MHz) with large footprint (typically a curvilinear probe) is ideal for the assessment of the aorta. • Begin in the midline in the transverse plane, with probe indicator aimed toward the patient’s right. Identify the proximal aorta, spine, IVC, and celiac axis. o The spine is an important landmark and without visualization it is possible to mistake a more superficial structure for the aorta • While maintaining gentle downward pressure on the transducer, slide the transducer caudally towards the umbilicus. The celiac axis appears first and due to its appearance, it is sometimes referred to as having a seagull appearance (Figure 1). Measure the proximal aorta at or above the celiac axis, in the anterior-posterior plane, from outer wall to outer wall. • Continue to slide the transducer caudally and identify the superior mesenteric artery (SMA). The SMA begins about 1 cm caudad to the celiac axis and is surrounded by hyperechoic tissue. It is sometimes referred to as a having a “mantle clock” appearance (Figure 2). Measure the mid aorta just distal to the SMA, in the anterior-posterior plane, from outer wall to outer wall. • Continue to slide the transducer caudally until you reach the aortic bifurcation, usually at the level of the umbilicus. The distal aorta is measured just proximal to the bifurcation, in the anterior-posterior plane, from outer wall to outer wall. • As one progresses distally towards the aortic bifurcation, the aorta becomes more superficial. Adjust depth as needed. • Scan past the bifurcation and measure each common iliac artery. • Return to the subcostal space and scan the aorta in the sagittal plane, with the probe indicator aimed towards the patient’s head. Identify the aorta with spinal stripe, celiac axis and SMA (Figure 3). •