What is the significance and recommended management of a bilateral lower extremity arterial duplex study showing normal flow, no occlusion or high‑grade stenosis, normal inflow at the groin, and normal resting and post‑exercise ankle‑brachial indices in a patient presenting with leg pain?

Normal Vascular Study in a Patient with Leg Pain: Significance and Management

A bilateral lower extremity arterial duplex study showing normal flow, no stenosis, normal inflow, and normal resting and post-exercise ankle-brachial indices effectively excludes hemodynamically significant peripheral arterial disease as the cause of leg pain, and management should focus on identifying alternative etiologies such as musculoskeletal disorders, venous insufficiency, neurogenic claudication, or chronic exertional compartment syndrome. 1

Interpretation of Normal Vascular Findings

What the normal study tells you:

• Resting ABI in the normal range (1.00–1.40) has 84–99% specificity for excluding PAD, meaning a normal value reliably rules out hemodynamically significant arterial occlusive disease 1
• Normal post-exercise ABI (no drop >20% or absolute ankle pressure decrease >30 mmHg) excludes exercise-induced arterial insufficiency and proximal stenoses that might be masked at rest 1
• Biphasic and triphasic waveforms throughout strongly exclude significant PAD, as triphasic pedal Doppler waveforms essentially rule out arterial compromise 2, 3
• Two-vessel runoff to the ankle-foot (posterior tibial and dorsalis pedis) with normal acceleration time at the groin confirms adequate arterial perfusion from aortoiliac inflow through tibial outflow 1

Sensitivity limitations to acknowledge:

• While ABI has high specificity (84–99%), sensitivity ranges from only 68–84%, meaning a small percentage of patients with PAD may have normal resting ABI 1
• However, the addition of normal post-exercise ABI and normal duplex waveforms throughout substantially increases the negative predictive value for excluding PAD 1

Differential Diagnosis for Leg Pain with Normal Vascular Study

With PAD effectively excluded, systematically evaluate these alternative causes:

Musculoskeletal Etiologies

• Osteoarthritis of hip or knee: Pain worsens with weight-bearing, improves with rest, associated with joint stiffness and reduced range of motion
• Lumbar spinal stenosis (neurogenic claudication): Pain radiates from back to legs, worsens with standing/walking, improves with sitting or forward flexion (shopping cart sign), often bilateral and associated with numbness
• Chronic exertional compartment syndrome: Tight, bursting pain in specific muscle compartments during exercise, relieved within 15–30 minutes of rest, common in younger active individuals

Venous Disorders

• Chronic venous insufficiency: Aching, heaviness, swelling that worsens throughout the day, improves with leg elevation, associated with varicosities or skin changes
• May-Thurner syndrome: Left leg predominant symptoms in younger women, positional component

Neurologic Causes

• Peripheral neuropathy: Burning, tingling, numbness in stocking-glove distribution, often worse at night
• Radiculopathy: Dermatomal pain distribution, associated with back pain and specific nerve root findings

Other Considerations

• Popliteal artery entrapment syndrome: Young athletic patients with calf claudication, normal ABI at rest but may become abnormal with provocative maneuvers
• Medication-induced myalgias: Statins, fibrates
• Inflammatory myopathies or systemic conditions

Recommended Management Algorithm

Immediate Clinical Assessment

Obtain focused history to distinguish etiologies:

• Pain characteristics: Sharp vs. aching vs. burning; location; radiation pattern
• Positional factors: Does forward flexion relieve symptoms (suggests spinal stenosis)? Does leg elevation help (suggests venous)? Does rest in any position relieve pain quickly?
• Timing: Worse at end of day (venous), worse at night (neuropathy), predictable with specific exercise distance (would suggest arterial but ruled out)
• Associated symptoms: Numbness, weakness, swelling, skin changes, back pain

Perform targeted physical examination:

• Spine examination: Range of motion, straight leg raise, focal tenderness
• Joint examination: Crepitus, effusion, range of motion limitations
• Neurologic examination: Strength testing, reflexes, sensory distribution
• Venous examination: Varicosities, edema, skin changes (hemosiderin deposition, lipodermatosclerosis)
• Compartment palpation: Firmness, tenderness of muscle compartments

Diagnostic Testing Based on Clinical Suspicion

If neurogenic claudication suspected:

• Obtain lumbar spine MRI to evaluate for spinal stenosis, disc herniation, or nerve root compression
• Consider referral to spine specialist or physiatry

If venous insufficiency suspected:

• Perform venous duplex ultrasound to assess for reflux and exclude deep venous thrombosis
• Consider referral to vascular surgery for venous intervention if severe

If musculoskeletal etiology suspected:

• Obtain plain radiographs of affected joints
• Consider MRI if soft tissue pathology suspected
• Refer to orthopedics or sports medicine

If chronic exertional compartment syndrome suspected:

• Refer to sports medicine or orthopedic surgery for compartment pressure testing
• Diagnosis requires pre- and post-exercise compartment pressure measurements

If peripheral neuropathy suspected:

• Check hemoglobin A1c, vitamin B12, thyroid function
• Consider electromyography/nerve conduction studies
• Refer to neurology if etiology unclear

Cardiovascular Risk Stratification Despite Normal PAD Testing

Even with normal vascular studies, address cardiovascular risk factors:

• A normal ABI does not eliminate cardiovascular risk; these patients may still have coronary or cerebrovascular disease 1
• Implement guideline-directed medical therapy for atherosclerosis risk factors: statin therapy for hyperlipidemia, blood pressure control, smoking cessation, diabetes management 1
• Consider screening for coronary artery disease if multiple risk factors present, particularly if patient has exertional symptoms

Common Pitfalls to Avoid

Do not assume PAD is the only cause of leg pain in older patients or those with risk factors:

• The presence of atherosclerosis risk factors does not mean leg pain must be vascular; normal vascular studies reliably exclude hemodynamically significant PAD 1

Do not repeat vascular testing without new clinical indication:

• A comprehensive normal vascular study (resting ABI, exercise ABI, duplex with waveforms) has high negative predictive value 1
• Repeating vascular studies is not indicated unless symptoms change significantly or new vascular findings emerge on examination

Do not overlook spinal stenosis in older patients:

• Neurogenic claudication is frequently misdiagnosed as vascular claudication; key distinguishing features are positional relief with forward flexion and lack of rapid relief with standing still 2

Do not dismiss symptoms as "nonspecific" without systematic evaluation:

• Normal vascular studies narrow the differential substantially and should prompt focused evaluation of alternative etiologies rather than reassurance alone

Do not forget that bilateral symptoms can still be unilateral pathology:

• Lumbar spinal stenosis commonly causes bilateral leg symptoms; May-Thurner syndrome affects the left leg preferentially 2

Follow-Up and Monitoring

Establish clear follow-up plan:

• Schedule follow-up after initial diagnostic workup for alternative etiologies is complete
• Provide specific return precautions: sudden onset of severe pain, color change, coolness, or loss of pulses would warrant urgent re-evaluation for acute arterial event
• Annual cardiovascular risk assessment and optimization of medical therapy regardless of PAD status 1