What is the best initial imaging test for a diabetic patient with a foot ulcer and diminished ankle pulses?

From the Guidelines

The best initial imaging test for a diabetic patient with a foot ulcer and diminished ankle pulses is duplex ultrasonography. This non-invasive vascular study should be performed first to evaluate arterial blood flow and identify the presence and extent of peripheral arterial disease, which is likely contributing to the patient's presentation. Duplex ultrasonography combines traditional ultrasound with Doppler technology to visualize blood vessels and measure blood flow velocity, providing information about both anatomy and function. It can detect arterial stenosis or occlusion that may be compromising blood flow to the affected foot. This test is preferred initially because it is readily available, cost-effective, does not use radiation or contrast agents, and can be performed safely even in patients with renal impairment (common in diabetics) 1.

Key Considerations

• The patient's clinical presentation, including a foot ulcer and diminished ankle pulses, suggests peripheral arterial disease, which duplex ultrasonography can help diagnose 1.
• Duplex ultrasonography is a non-invasive and cost-effective initial imaging test that can provide valuable information about arterial blood flow and potential stenosis or occlusion 1.
• If significant vascular disease is identified on ultrasound, further imaging such as CT angiography or conventional angiography may be warranted to plan revascularization procedures 1.
• Early detection and management of arterial insufficiency are crucial in diabetic foot ulcers to promote healing and prevent amputation 1.

Additional Imaging Tests

• MRI, WBC scintigraphy, or [18F]FDG PET/CT may be considered for further evaluation of the foot ulcer, particularly if there is suspicion of osteomyelitis or soft tissue infection 1.
• However, these tests are not typically used as the initial imaging test and are usually reserved for cases where the diagnosis is uncertain or further evaluation is needed 1.

Clinical Guidelines

• The IWGDF/IDSA guidelines recommend using MRI for patients who require a more sensitive or specific imaging study, or when the diagnosis of osteomyelitis is uncertain with less advanced tests 1.
• The Society for Vascular Surgery and other organizations also recommend using duplex ultrasonography as an initial imaging test for patients with suspected peripheral arterial disease 1.

From the Research

Initial Imaging Test for Diabetic Patient with Foot Ulcer and Diminished Ankle Pulses

The best initial imaging test for a diabetic patient with a foot ulcer and diminished ankle pulses is a topic of interest due to the high risk of peripheral arterial disease (PAD) in this population.

• The patient's symptoms, including a one-week history of fever, swelling, and redness of the right foot, along with a draining ulcer on the ball of the right foot, suggest a possible infection and PAD.
• Considering the patient's diabetes and peripheral neuropathy, it is essential to choose an imaging test that can accurately assess the peripheral vasculature without requiring arterial catheterization, nephrotoxic contrast, or ionizing radiation.

Contrast-Enhanced Magnetic Resonance Angiography (CE-MRA)

• CE-MRA is a suitable option for evaluating peripheral vascular disease, as it allows for accurate and detailed assessment of peripheral vasculature 2.
• A study published in 2013 found that CE-MRA had a pooled sensitivity of 86% and specificity of 93% in differentiating the extent of disease in patients with infragenicular PAD and diabetes 3.
• Another study in 2010 compared the diagnostic accuracy of CE-MRA and duplex ultrasound in patients with peripheral vascular disease, finding that CE-MRA had a sensitivity of 91% and specificity of 99% in depicting stenosis >50% 4.

Duplex Ultrasound

• Duplex ultrasound is another non-invasive technique that can be used to evaluate peripheral vascular disease.
• The 2010 study mentioned earlier found that duplex ultrasound had a sensitivity of 81.4% and specificity of 99% in depicting stenosis >50% 4.

Recommendation

• Based on the available evidence, CE-MRA appears to be a suitable initial imaging test for a diabetic patient with a foot ulcer and diminished ankle pulses, due to its high sensitivity and specificity in evaluating peripheral vascular disease 2, 3, 4.
• However, the choice of imaging test may ultimately depend on the individual patient's circumstances and the availability of imaging modalities.