Antero-posterior Diameter

Finally, measure the antero-posterior diameter of the aorta.

The measurements should be from outer wall to outer wall of the vessel. Any clot or false lumen should be ignored when measuring.

Be careful to avoid two pitfalls:

One is taking a non-perpendicular view of the vessel, thereby creating a ‘salami slice’ with over-estimation of the diameter. As the aorta is angled against the lumbar lordosis, the probe often needs to point slightly caudally to overcome this (image bottom left).

The other is failing to appreciate a tortuous aorta, though this only creates significant problems if transverse measurements are taken (image bottom right).