Normal Femoral Artery Diameter on Ultrasound, CT & MRI
The femoral artery, arising from the external iliac artery at the inguinal ligament, is the principal arterial supply to the lower extremity. It divides into the common femoral artery (CFA) and, distally, the superficial femoral artery (SFA) and profunda femoris. Accurate diameter measurement is essential for procedural planning, surveillance of aneurysmal disease, and assessment of peripheral arterial disease.
Normal Reference Values
| Orientation | Location | Measurement |
|---|---|---|
| Axial | Common | 6.6-9.6 mm |
| Axial | Superficial | 4.3-7.2 mm |
Clinical Significance
The common femoral artery normally measures 6.6–9.6 mm in axial diameter, while the superficial femoral artery measures 4.3–7.2 mm. A diameter exceeding 1.5× the expected normal value is the conventional threshold for defining a true aneurysm. Femoral artery aneurysms, though less common than popliteal aneurysms, carry significant risk of thromboembolism and limb ischemia.
Conversely, focal luminal narrowing or diffuse reduction in caliber suggests atherosclerotic stenosis or occlusive disease. Comparison with the contralateral side is important, as asymmetry may be the first indicator of hemodynamically significant disease. Post-procedural pseudoaneurysm following arterial access is another key diagnosis to consider when a pulsatile groin mass is encountered.
- Femoral artery aneurysm — diameter >1.5× normal; risk of thromboembolism
- Atherosclerotic occlusive disease — diffuse or focal luminal reduction
- Post-catheterization pseudoaneurysm — pulsatile perivascular collection at access site
- Arteriovenous fistula — post-procedural; associated with venous arterialization
- Vasculitis — irregular wall thickening with luminal irregularity
Reference: Shionoya S. Noninvasive diagnostic techniques in vascular disease. Int Angiol. 6 (3): 213-21.
Imaging Notes
Ultrasound is the first-line modality for femoral artery measurement. Diameter should be assessed in the axial plane using B-mode imaging, measured from inner wall to inner wall (lumen diameter) or outer wall to outer wall (total diameter) depending on clinical context. Avoid oblique angulation, which can overestimate the true diameter. Duplex Doppler adds hemodynamic information about stenosis severity.
CT angiography allows precise axial measurement of the CFA and SFA with multiplanar reformats; measurements should be taken perpendicular to the vessel centerline to avoid overestimation. MRI with contrast-enhanced MR angiography provides excellent soft-tissue characterization and is preferred when radiation avoidance is indicated, though spatial resolution is slightly lower than CTA. On both cross-sectional modalities, calcified plaque may obscure the true lumen, requiring careful window/level adjustment.