What is the appropriate workup for a patient presenting with lower leg pain?

Workup for Lower Leg Pain

Begin with a focused vascular history and physical examination, followed by resting ankle-brachial index (ABI) measurement as the initial diagnostic test to establish or exclude peripheral artery disease (PAD), which is the most critical diagnosis to identify given its implications for morbidity and mortality. 1

Initial Clinical Assessment

History - Key Elements to Elicit

• Characterize the pain pattern: Ask specifically about pain location (hip/buttock/thigh vs. calf vs. foot), quality (aching, sharp, lancinating, tight/bursting), timing (at rest vs. with exertion), and what relieves it (rest, position change, leg elevation) 1

• Assess for claudication: Determine if pain occurs predictably with walking a certain distance and resolves within 10 minutes of rest, which suggests vascular claudication 1

• Screen for critical limb ischemia (CLI) features: Ask about rest pain (especially worse when supine/at night), non-healing wounds, or tissue loss 1

• Document atherosclerotic risk factors: Smoking history, diabetes, hypertension, hyperlipidemia, family history of atherosclerosis 1

• Identify high-risk features: Diabetes with neuropathy, chronic renal failure, or signs of infection warrant urgent evaluation 1

Physical Examination - Required Components

• Remove all lower extremity garments including shoes and socks to perform a complete examination 1

• Palpate all four lower extremity pulses bilaterally (femoral, popliteal, dorsalis pedis, posterior tibial) and grade as: 0=absent, 1=diminished, 2=normal, 3=bounding 1

  • Presence of all four pedal pulses bilaterally makes PAD unlikely 1

• Auscultate for bruits over femoral arteries and abdomen to detect turbulent flow from stenoses 1

• Inspect for vascular insufficiency signs: Elevation pallor, dependent rubor, asymmetric hair growth, calf muscle atrophy 1

• Assess for peripheral neuropathy in patients with diabetes 1

Diagnostic Testing Algorithm

First-Line Test: Resting ABI

Obtain resting ABI with or without segmental pressures and waveforms in all patients with suspected PAD based on history or physical examination findings. 1

• Measure systolic blood pressures at both brachial arteries and at ankles (dorsalis pedis and posterior tibial) using Doppler 1
• Calculate ABI for each leg by dividing the higher ankle pressure by the higher arm pressure 1

Interpret ABI results as follows: 1

• ≤0.90 = Abnormal (diagnostic of PAD)
• 0.91-0.99 = Borderline
• 1.00-1.40 = Normal
• >1.40 = Noncompressible (proceed to toe-brachial index)

Second-Line Testing Based on ABI Results

If ABI >1.40 (noncompressible arteries):

• Measure toe-brachial index (TBI) to diagnose PAD, as digital arteries are rarely noncompressible 1
• TBI ≤0.70 is diagnostic of PAD 1
• This is particularly important in patients with longstanding diabetes or advanced chronic kidney disease 1

If ABI is normal (1.00-1.40) or borderline (0.91-0.99) but exertional leg symptoms persist:

• Perform exercise treadmill ABI testing to objectively measure functional limitation and diagnose PAD 1
• A decline in ABI after exercise confirms PAD as the cause of symptoms 1
• If treadmill unavailable, pedal plantarflexion ABI test is a reasonable alternative 1

If ABI is abnormal (≤0.90) and patient has claudication:

• Consider exercise treadmill ABI testing to objectively assess functional status and document magnitude of symptom limitation 1
• This provides baseline data for monitoring response to therapy 1

Additional Perfusion Assessment for Suspected CLI

If patient has nonhealing wounds or gangrene with normal/borderline ABI (0.90-1.40):

• Obtain TBI with waveforms, transcutaneous oxygen pressure (TcPO2), or skin perfusion pressure (SPP) to diagnose CLI 1
• Toe pressure <30 mm Hg decreases likelihood of wound healing 1

If patient has CLI features with abnormal ABI (≤0.90) or noncompressible arteries:

• TBI with waveforms, TcPO2, or SPP can further evaluate local perfusion 1

Anatomic Imaging - Reserved for Revascularization Candidates

Do not obtain anatomic imaging unless revascularization is being considered. 1

For symptomatic PAD patients being considered for revascularization:

• Duplex ultrasound, CTA, or MRA is useful to diagnose anatomic location and severity of stenosis 1

For CLI patients being considered for revascularization:

• Invasive angiography is the recommended modality 1

Differential Diagnosis Considerations

If vascular testing is normal, consider these alternative causes based on clinical features: 1, 2

• Spinal stenosis: Bilateral buttock/posterior leg pain and weakness, worse with standing/extending spine, relieved by lumbar flexion 1, 2
• Venous claudication: Tight, bursting pain in entire leg, subsides slowly, relieved by elevation, history of deep vein thrombosis 1, 2
• Chronic compartment syndrome: Tight, bursting pain after strenuous exercise in calf muscles, subsides very slowly, typically in athletes 1, 2
• Hip or ankle arthritis: Aching pain after variable exercise, not quickly relieved by rest, improved when not bearing weight 1, 2
• Nerve root compression: Sharp lancinating pain radiating down leg, induced by sitting/standing/walking, history of back problems 1

Critical Clinical Pitfalls

• Patients with diabetes and CLI may have no pain due to neuropathy but still have severe tissue loss requiring urgent evaluation 1

• Patients at risk for CLI (diabetes, neuropathy, chronic renal failure, infection) who develop acute limb symptoms represent vascular emergencies and require immediate assessment by a vascular specialist 1

• Do not rely on ABI alone in diabetic patients or those with chronic kidney disease due to high incidence of noncompressible arteries; obtain TBI 1

• Expedite evaluation if clinical history suggests rapid progression as early revascularization may prevent irreversible tissue loss 1