In a 69-year-old man with a 4‑day history of acute left tibia and fibula and ankle pain and swelling, normal serum uric acid, no erythema or severe tenderness, and no recent trauma (remote gunshot wound 30 years ago), what is the appropriate diagnostic work‑up and initial management?

Diagnostic Work-Up and Initial Management

In this 69-year-old man with 4 days of acute left tibia/fibula and ankle pain and swelling, normal uric acid, no erythema or severe tenderness, and remote trauma history, the most critical first step is to obtain a venous duplex ultrasound to rule out deep venous thrombosis (DVT), which is the most dangerous diagnosis that must be excluded immediately. 1, 2

Immediate Diagnostic Priority: Rule Out DVT

Why DVT Must Be Excluded First

• Unilateral leg swelling with pain is a classic presentation of DVT, which affects 1-2% of hospitalized patients and can lead to fatal pulmonary embolism in approximately 200,000 patients annually in the United States 3
• The 4-day duration of symptoms, unilateral distribution, and location in the calf region (tibia/fibula area) are highly consistent with DVT 2, 3
• The remote gunshot wound 30 years ago may have caused chronic venous damage or scarring that predisposes to thrombosis 3

Clinical Assessment for DVT Pre-Test Probability

• Apply a clinical decision rule to stratify DVT probability as "unlikely" or "likely" based on: unilateral leg swelling (present in this patient), localized tenderness along deep venous system, entire leg swelling, calf swelling >3 cm compared to asymptomatic leg, pitting edema confined to symptomatic leg, collateral superficial veins, active cancer, paralysis/paresis/recent immobilization, recently bedridden >3 days or major surgery within 12 weeks, and alternative diagnosis as likely or more likely than DVT 2
• If DVT is "likely" based on clinical features, proceed directly to compression ultrasound 2
• If DVT is "unlikely," obtain D-dimer testing first; if elevated, proceed to compression ultrasound 2

Definitive DVT Imaging

• Obtain venous duplex ultrasonography of the entire leg (whole-leg ultrasound) to evaluate both proximal veins (popliteal, femoral) and calf veins (tibial, peroneal, gastrocnemius, soleal) 1, 4
• Compression ultrasonography is sensitive and specific for proximal DVT in symptomatic patients, though less sensitive for isolated calf-vein DVT 3
• If initial ultrasound is negative but clinical suspicion remains high, serial compression ultrasound at 2-3 days or single deferred whole-leg ultrasound should be performed 1, 4

Secondary Diagnostic Considerations After DVT Is Excluded

Gout Remains on the Differential Despite Normal Uric Acid

• Approximately 10% of patients with acute gout have normal serum uric acid levels during an attack because uric acid behaves as a negative acute phase reactant during inflammation 5
• However, the absence of erythema and severe tenderness makes acute gout significantly less likely, as gout characteristically causes rapid development of severe pain, swelling, tenderness, and overlying erythema reaching maximum intensity within 6-24 hours 6, 5
• The 4-day duration without erythema or severe tenderness argues strongly against acute gout 6, 5

When to Pursue Crystal Arthropathy Work-Up

• If DVT is excluded and clinical suspicion for crystal arthropathy persists, obtain joint aspiration with synovial fluid analysis for monosodium urate crystals (gout) or calcium pyrophosphate crystals (pseudogout) using polarized light microscopy 5
• Gram stain and culture must be performed on any joint aspirate even if crystals are identified, as crystal arthritis and septic arthritis can coexist 6, 5
• If joint aspiration cannot be performed, ultrasound imaging should be obtained to look for the "double contour sign" (74% sensitivity, 88% specificity for gout) or chondrocalcinosis suggesting pseudogout 5

Diabetic Foot Infection Considerations

• If the patient has diabetes, evaluate for diabetic foot infection using the IDSA/IWGDF classification system, which requires at least two of the following: local swelling/induration, erythema >0.5 cm around wound, local tenderness/pain, local warmth, or purulent discharge 6
• The absence of erythema, severe tenderness, and purulent discharge makes diabetic foot infection unlikely 6
• Perform probe-to-bone test if there is any open wound; a negative test in low-risk patients largely rules out osteomyelitis 6

Soft Tissue Infection or Cellulitis

• Evaluate for signs of soft tissue infection including erythema extending >0.5 cm from any wound margin, warmth, tenderness, and systemic signs (fever >38°C, heart rate >90 bpm, WBC >12,000/mm³) 6
• The absence of erythema and fever makes cellulitis or soft tissue infection less likely 6

Essential Laboratory Tests

• Complete blood count with differential to assess for leukocytosis suggesting infection or inflammatory process 6
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to evaluate inflammatory markers; markedly elevated ESR is suggestive of osteomyelitis if bone infection is suspected 6
• Serum creatinine and estimated glomerular filtration rate (eGFR) to assess renal function, as chronic kidney disease increases risk for both DVT complications and gout (relative risk 4.95 for gout) 5
• Repeat serum uric acid after acute phase resolves if gout remains in differential, as levels may normalize during acute inflammation 5

Imaging Studies

• Plain radiographs of the left tibia/fibula and ankle to evaluate for chronic changes from remote gunshot wound, assess for subcortical cysts or erosions suggesting chronic gout, rule out fracture, and identify any retained foreign body or chronic osteomyelitis 6, 5
• Venous duplex ultrasound as described above is the priority imaging study 1, 2

Initial Management Pending Diagnostic Results

• Do not initiate anticoagulation until DVT work-up is complete unless clinical probability is extremely high and ultrasound will be delayed 2
• Elevate the affected leg and apply compression stockings if DVT is ruled out 2
• Avoid anti-inflammatory medications until infection is definitively excluded 6
• If DVT is confirmed, initiate anticoagulation with direct oral anticoagulant (apixaban or rivaroxaban without initial parenteral therapy, or dabigatran/edoxaban after initial parenteral anticoagulant) as DOACs are preferred over warfarin for safety, efficacy, and convenience 2

Common Pitfalls to Avoid

• Do not assume this is gout based on location alone; the ankle and calf are not typical sites for initial gout presentation, and normal uric acid combined with absence of erythema makes gout unlikely 6, 5
• Do not delay DVT evaluation because the patient lacks classic risk factors; the remote gunshot wound may have caused chronic venous damage predisposing to thrombosis 3
• Do not diagnose cellulitis without erythema; the absence of redness makes soft tissue infection very unlikely 6
• Do not start empiric antibiotics without clear evidence of infection, as this may mask a more serious underlying condition 6