Vascular Abnormalities
What to know
Abdominal aortic aneurysm: measure outer wall to outer wall, perpendicular to the vessel, in the anteroposterior plane; mural thrombus is included in the diameter. A diameter of 3.0 cm or more defines an aneurysm.
Aortic dissection shows an intimal flap separating true and false lumens; the false lumen is usually larger with slower flow and may thrombose. Renal artery stenosis produces focal velocity elevation with post-stenotic turbulence and a tardus-parvus intrarenal waveform. Portal hypertension shows a portal vein over 13 mm, splenomegaly, ascites, varices, and a recanalized umbilical vein. Portal vein thrombosis is echogenic material in the lumen with absent flow; tumor thrombus shows internal arterial flow. Budd-Chiari syndrome shows hepatic vein narrowing or thrombosis, caudate hypertrophy, and collateral spider-web veins. Pseudoaneurysms show a yin-yang color pattern and a to-and-fro neck waveform; arteriovenous fistulas show high-velocity low-resistance flow with arterialized veins.
Traps
Inner-to-inner measurement underestimates aneurysms. Never diagnose portal vein thrombosis on grayscale alone-confirm with color and spectral Doppler.
Rule of thumb
Aneurysms of 5.0–5.5 cm in men, or rapid growth, prompt referral for repair.
Worked example
A 4.2 cm infrarenal aorta measured outer-to-outer with mural thrombus included is an aneurysm requiring surveillance, not immediate surgery.