What is the role of Duplex (ultrasound) for diagnosing lower limb vascular stenosis?

From the Guidelines

Doppler ultrasound is the recommended first-line imaging test for evaluating lower limb vascular stenosis due to its non-invasive nature, wide availability, and absence of radiation exposure. The procedure involves applying ultrasound gel to the skin and using a handheld transducer to assess blood flow through the arteries and veins of the legs. During the examination, patients may be asked to lie still while the technician evaluates blood flow at rest, followed by measurements after exercise or specific maneuvers to detect flow abnormalities that appear only during activity. The test typically takes 30-60 minutes and requires no special preparation, though comfortable, loose-fitting clothing that allows access to the legs is advisable. Doppler ultrasound works by measuring the change in frequency of sound waves as they bounce off moving red blood cells, providing information about blood flow velocity, direction, and the presence of blockages. It can effectively identify stenosis (narrowing), occlusions (complete blockages), and quantify the degree of vessel narrowing through measurements like peak systolic velocity ratios. For patients with suspected peripheral arterial disease, the ankle-brachial index (ABI) is often performed alongside Doppler studies to compare blood pressure in the arms and ankles, with values below 0.9 indicating significant stenosis, as supported by the most recent guidelines 1.

Key Points

• Doppler ultrasound has a sensitivity and specificity of approximately 90% to 95% for diagnosing stenoses >50% in diameter from the iliac arteries to the popliteal arteries 1.
• The use of color Doppler improves accuracy, but accuracy is diminished in examinations of the iliac arteries if bowel gas or tortuosity obscures the iliac vessels 1.
• Duplex US is useful for choosing between endovascular and surgical revascularization, but it is not satisfactory for evaluating tibial arteries for distal bypass or choosing specific treatment plans with a high degree of confidence 1.
• The advantages of duplex US include its portability and lack of IV contrast agent, but disadvantages include limited sonographic windows and potential underestimation of the extent of disease when multiple “tandem” stenotic segments are present in series 1.

Recommendations

• Doppler ultrasound should be used as the initial imaging test for patients with suspected lower limb vascular stenosis 1.
• ABI and arterial duplex ultrasound are recommended for patients with PAD who have undergone lower extremity revascularization with new lower extremity signs or symptoms 1.
• Duplex US should be performed by a highly skilled sonographer and may require over an hour to perform, depending on the complexity of the case 1.

From the Research

Doplex for Lower Limb Vascular Stenosis

• The use of Doplex for lower limb vascular stenosis is not directly mentioned in the provided studies. However, the studies discuss various treatment options for lower limb ischemia and peripheral artery disease (PAD).
• According to 2, effective medical management is key in reducing the risk of major adverse cardiovascular events and major adverse limb events in patients with PAD.
• The study 3 discusses the potential role of endovascular interventions for young patients with lower-limb ischemia, including catheter-directed thrombolysis and angioplasty and stenting procedures.
• The use of antiplatelet agents and anticoagulants is well established in the treatment of arteriosclerosis, as discussed in 4 and 5.
• A fast-track thrombolysis protocol for acute limb ischemia is described in 6, which includes periadventitial lidocaine injection, contrast arteriography, pharmacomechanical rheolytic thrombectomy, tissue plasminogen activator infusion, balloon maceration of the thrombus, and placement of a stent if necessary.
• The interaction between antiplatelet therapy and lipid-lowering agents (statins and PCSK9 inhibitors) is discussed in 5, highlighting the synergistic actions of these drugs in reducing the incidence of atherothrombotic vascular events.

Treatment Options for Lower Limb Vascular Stenosis

• Endovascular interventions, such as catheter-directed thrombolysis and angioplasty and stenting procedures, may be beneficial for patients with symptoms secondary to atherosclerosis 3.
• Antiplatelet agents and anticoagulants, such as aspirin and clopidogrel, are effective in reducing the risk of major adverse cardiovascular events and major adverse limb events 2, 4, 5.
• A fast-track thrombolysis protocol, as described in 6, may be a safe and effective treatment option for acute limb ischemia.

Medical Management of Peripheral Artery Disease

• Effective medical management is key in reducing the risk of major adverse cardiovascular events and major adverse limb events in patients with PAD 2.
• The use of antiplatelet agents and anticoagulants, as well as medications to control low-density lipoprotein cholesterol, blood pressure, and diabetes, is essential in the medical management of PAD 2, 4, 5.