How to manage an adult patient with no significant medical history presenting with unilateral intense leg pain?

Management of Unilateral Intense Leg Pain in Adults

Immediately measure the ankle-brachial index (ABI) and assess for life-threatening conditions including deep vein thrombosis (DVT) and critical limb ischemia (CLI), as these represent vascular emergencies requiring urgent specialist evaluation. 1, 2

Initial Emergency Assessment

Rule Out Life-Threatening Conditions First

• Assess for DVT by examining for unilateral extremity swelling (present in 80% of cases), pain (75%), and erythema (26%), with venous ultrasound as the preferred initial diagnostic test 1
• Measure resting ABI immediately in all patients with leg pain to exclude peripheral arterial disease, with ABI ≤0.90 confirming PAD 1, 2
• Evaluate for CLI features including rest pain (worse when supine, improves with leg dependency), non-healing wounds, or tissue loss—these patients require immediate vascular specialist assessment 3, 2
• Patients at risk for CLI who develop acute limb symptoms represent vascular emergencies and must be assessed immediately by a vascular specialist 3, 2

Interpret ABI Results

• ABI ≤0.90 = Abnormal and diagnostic of PAD 2
• ABI 0.91-0.99 = Borderline—consider exercise treadmill ABI testing if symptoms persist 2
• ABI 1.00-1.40 = Normal 2
• ABI >1.40 = Noncompressible vessels (common in diabetes)—proceed to toe-brachial index instead 2

Characterize the Pain Pattern

Vascular vs. Neurogenic Claudication

• Vascular claudication occurs predictably with walking a specific distance, resolves within 10 minutes of rest, and is not present at rest 2, 4
• Neurogenic claudication (spinal stenosis) presents with pain during standing/walking that is relieved by sitting or forward flexion 1
• Critical limb ischemia causes rest pain that worsens when supine and improves with leg dependency, typically requiring narcotic analgesia 3

Neurogenic Causes

• Pain radiating below the knee in sciatic distribution suggests nerve root compression 1
• Perform straight leg raise (SLR) test: 91% sensitivity but only 26% specificity for disc herniation 1
• Crossed SLR test is more specific: 88% specificity and 29% sensitivity for disc herniation 1
• Conduct neurological examination for motor/sensory deficits 1

Diagnostic Algorithm

Step 1: Immediate Vascular Assessment

• Palpate all lower extremity pulses bilaterally and auscultate for femoral bruits 4
• Inspect skin for pallor with leg elevation, skin changes, or tissue loss 4
• Obtain resting ABI with or without segmental pressures in all patients with suspected PAD 2

Step 2: If ABI is Abnormal (≤0.90)

• Document atherosclerotic risk factors including smoking, diabetes, hypertension, hyperlipidemia 2
• Consider exercise treadmill ABI testing if patient has claudication to objectively assess functional status 2
• Do NOT obtain anatomic imaging (duplex ultrasound, CTA, MRA) unless revascularization is being considered 2

Step 3: If ABI is Normal but Symptoms Persist

• Perform exercise treadmill ABI testing to diagnose PAD that manifests only with exertion 2
• Assess for hip pathology (femoroacetabular impingement, acetabular dysplasia, labral tears) which can present as sharp leg pain without groin pain 1
• Perform flexion-adduction-internal rotation test—negative result helps rule out hip-related pain 1

Step 4: Imaging Only When Indicated

• Reserve imaging for severe/progressive neurological deficits or persistent symptoms despite conservative treatment 1
• For CLI patients being considered for revascularization, invasive angiography is the recommended modality 2

Pain Management

Multimodal Analgesia Approach

Implement a multimodal analgesia strategy including acetaminophen, gabapentinoids, NSAIDs, lidocaine patches, with opioids reserved only for breakthrough pain at the lowest effective dose for the shortest period 3

• Consider adding NSAIDs for severe pain while accounting for potential adverse events and drug interactions 3
• For CLI with rest pain, narcotic medications are typically required for adequate analgesia 3
• Implement non-pharmacological measures such as immobilizing limbs and applying ice packs in conjunction with drug therapy 3

Regional Analgesia for Specific Conditions

• For acute hip fractures, peripheral nerve blocks at presentation reduce preoperative and postoperative opioid use 3
• Epidural analgesia and regional anesthesia can control severe pain in selected patients with acute fractures 3

Critical Clinical Pitfalls

• Diabetic patients with CLI may have no pain due to neuropathy but still have severe tissue loss requiring urgent evaluation 3, 2
• Do not rely on ABI alone in diabetic patients or those with chronic kidney disease due to noncompressible arteries—obtain toe-brachial index 2
• Left leg DVT has particularly high risk (May-Thurner syndrome) with sudden onset 1
• If DVT is confirmed, immediate anticoagulation is required 1

Urgent Referral Criteria

• Immediate vascular specialist referral for patients with CLI features (rest pain, tissue loss, non-healing wounds) 3, 2
• Systemic antibiotics should be initiated promptly in patients with CLI, skin ulcerations, and evidence of limb infection 3
• Refer to specialized wound care providers for patients with CLI and skin breakdown 3