Aneurysmal Disease of the Aorta and Peripheral Arteries
Definition and measurement
An arterial aneurysm is a focal, permanent dilation exceeding 3.0 cm in the aorta or 50% of expected normal diameter elsewhere. Most abdominal aortic aneurysms (AAAs) are infrarenal and degenerative, driven by medial proteolysis. Measure on CT from outer wall to outer wall, perpendicular to the vessel axis; ultrasound uses leading-edge to leading-edge. A favorite exam trap is comparing a 5.3 cm ultrasound measurement with a 4.9 cm CT measurement - technique matters, and cross-sectional imaging is required before repair.
Timing of intervention
Offer elective repair for infrarenal AAA at 5.5 cm in men and 5.0 cm in women, for growth of 1.0 cm per year (0.5 cm in six months), or for symptoms. EVAR has an early survival advantage over open repair in randomized trials, but late mortality converges and reintervention is more frequent, so anatomy and life expectancy drive selection. Typical instructions-for-use anatomy requires a proximal neck of 10–15 mm, neck diameter 18–32 mm, angulation under 60 degrees, and iliac access of 7–8 mm.
Peripheral and special aneurysms
The popliteal artery is the commonest peripheral aneurysm; about half are bilateral, many coexist with AAA, and repair is advised at 2 cm or when thrombus or distal embolization is present. Mycotic aneurysms are saccular, often Salmonella or Staphylococcus, and need debridement with extra-anatomic or in-situ reconstruction. Inflammatory aneurysms show a thick periaortic cuff and ureteral entrapment - avoid extensive dissection.
Worked example: a 72-year-old man with an asymptomatic 5.2 cm AAA that grew 0.6 cm in six months meets the growth criterion and should be offered repair rather than continued surveillance.