An elderly man presented with breathlessness and was noted to be in ventricular tachycardia. Examination revealed an abdominal mass.
AAA case 3
A large abdominal aortic aneurysm with mural thrombus was seen. The images show the correct and incorrect measurements of the aneurysm size.
A large AAA is present.
Errors in measuring the abdominal aorta can occur from measuring other structures (such as IVC, spine, SMA). To prevent this, the aorta must be definitely identified by it’s anatomical relationships (anterior to the spine, to the left of the IVC, with anterior branches (although they may be difficult to identify so this rarely helps in difficult cases)). Note that the IVC also pulsates, so this cannot be used to distinguish the aorta (and the double venous pulsation is not present if the patient is in atrial fibrillation). If thrombus is present then this must be included in the measurement (outer wall to outer wall).
In addition, the abdominal aorta may be impossible to view through it’s entire length, due to pain, guarding, gas and body habitus. In these circumstances the scan must be reported as “unable to exclude an abdominal aortic aneurysm”. Beginners should not see this as a failing and should note that even experienced sonologists cannot always obtain adequate images.