Indications
Intermittent claudication, rest pain or tissue loss (critical limb ischaemia), reduced or absent peripheral pulses, follow-up after surgical or endovascular revascularisation, screening in patients with multiple cardiovascular risk factors, and suspected popliteal or femoral aneurysm.
Equipment and patient position
- Linear array transducer 5–12 MHz for the common and superficial femoral, popliteal and calf vessels in patients of normal build; a curvilinear transducer 2–5 MHz may be needed for the iliac arteries and in patients with a thick abdominal wall.
- Patient supine with slight external rotation and abduction of the hip for the femoral segment; for the popliteal artery and calf vessels either prone, or supine with the knee flexed in the "frog-leg" position, according to what the patient can tolerate.
- A comparative bilateral examination, even when symptoms are unilateral.
Systematic scanning
3.1 · Iliac arteries
An abdominal approach with a curvilinear transducer, from the aortic bifurcation along the common and external iliac arteries to the inguinal ligament. Bowel gas and body habitus may limit the window: apply gradual transducer pressure to displace the bowel loops.
3.2 · Common, superficial and deep femoral arteries
From the inguinal ligament the common femoral artery is followed to its division into the superficial femoral artery (running anteromedially in the thigh, within the adductor canal) and the deep femoral artery (the main branch, to be followed for a short proximal segment: it is the principal collateral pathway when the superficial femoral artery is occluded).
3.3 · Popliteal artery
Followed in the popliteal fossa to its division into the tibioperoneal trunk and the anterior tibial artery. This is the commonest site for aneurysms (see section 5).
3.4 · Calf vessels
Anterior tibial artery (running anterolaterally, between tibia and fibula), posterior tibial and peroneal arteries (running posteriorly and deep, often requiring transducer pressure to approach the vascular plane). They are followed to the ankle when clinically indicated (critical limb ischaemia, planning of distal revascularisation).
Flow profile and stenosis criteria
The pulsed-wave Doppler flow profile is the first indicator, even qualitatively, of steno-obstructive disease proximally:
| Pattern | Meaning |
|---|---|
| Triphasic | Normal: systolic peak, brief early diastolic reversal, and a small late antegrade component. |
| Biphasic | Loss of the early diastolic reversal: possible mild to moderate proximal stenosis, or increased distal compliance. |
| Damped monophasic | Complete loss of the negative diastolic component with delayed systolic upstroke: significant proximal stenosis or occlusion. |
At the site of suspected stenosis the local PSV is measured and compared with the PSV of the normal segment immediately proximal: a velocity ratio (PSV ratio) ≥ 2 conventionally corresponds to a stenosis ≥ 50%, the haemodynamically relevant threshold. Colour Doppler shows associated aliasing and post-stenotic turbulence.
Assessment for aneurysm
The popliteal artery is the commonest peripheral site of aneurysm: measure the maximum anteroposterior diameter in the transverse plane, perpendicular to the axis of the vessel, and document any mural thrombus. The common femoral artery is the second commonest site. When a popliteal aneurysm is found, the contralateral popliteal artery should always be assessed as well, given how often the condition is bilateral.
What to measure and document
- Flow profile (triphasic, biphasic or monophasic) for each segment examined.
- PSV at the sites of suspected stenosis and in the proximal segment, with the velocity ratio.
- Site and extent of occlusions, with any distal reconstitution of flow through collateral vessels.
- Maximum diameter of any aneurysmal dilatation (femoral, popliteal), with its length and any mural thrombus.
- Findings after previous revascularisation (bypass, angioplasty or stent): patency, velocities within the graft, and any anastomotic stenosis.