A 52-year-old woman presents with a 3-day history of acute onset swelling and pain in the left lower limb. She returned from a 12-hour flight 5 days ago. On examination, the left calf is swollen, warm, and tender. Homan's sign is positive. D-dimer is elevated at 850 ng/mL. Compression ultrasonography shows non-compressible veins in the popliteal and femoral segments with echogenic thrombus. What is the most appropriate next step in management?

Explanation

## Diagnosis and Pathophysiology This patient has **acute proximal deep vein thrombosis (DVT)** confirmed by compression ultrasonography. The clinical presentation—immobility during air travel, acute calf swelling, warmth, tenderness, and positive Homan's sign—combined with imaging evidence of non-compressible veins with thrombus in the popliteal and femoral segments is diagnostic. **Key Point:** Proximal DVT (involving popliteal vein or above) carries a 40–50% risk of pulmonary embolism if untreated and mandates immediate anticoagulation. ## Management Algorithm ```mermaid flowchart TD A[Acute DVT confirmed on ultrasound]:::outcome --> B{Proximal or distal?}:::decision B -->|Proximal| C[Anticoagulation immediately]:::action B -->|Distal| D[Consider anticoagulation or surveillance] C --> E[UFH or LMWH loading]:::action E --> F[Transition to warfarin or DOAC]:::action F --> G[Target INR 2-3 for warfarin]:::outcome H{Contraindication to anticoagulation?}:::decision H -->|Yes| I[IVC filter]:::action H -->|No| J[Proceed with anticoagulation]:::action ``` ## Standard Anticoagulation Regimen | Agent | Loading/Initiation | Duration | Notes | |-------|-------------------|----------|-------| | **UFH** | 80 U/kg IV bolus, then 18 U/kg/hr infusion | 5–7 days | aPTT monitoring; reversible; preferred in renal failure | | **LMWH** | Weight-based SC (e.g., enoxaparin 1 mg/kg BD) | 5–7 days | Predictable kinetics; preferred outpatient | | **Warfarin** | Start 5 mg daily (adjust by INR) | 3 months minimum | Target INR 2–3; overlap with heparin 5–7 days | | **DOAC** | Apixaban 5 mg BD or rivaroxaban 15 mg daily | 3 months minimum | No monitoring; direct oral anticoagulant | **High-Yield:** Proximal DVT requires **immediate anticoagulation** to prevent PE. Thrombolysis is reserved for massive PE or limb-threatening thrombosis (phlegmasia cerulea dolens), not routine DVT. ## Why Anticoagulation Is Correct 1. **Prevents thrombus propagation** and embolization to lungs 2. **Allows endogenous fibrinolysis** to occur over days to weeks 3. **Standard of care** per ACCP guidelines (American College of Chest Physicians) and ISCVS recommendations 4. **No contraindication** evident in this patient (no active bleeding, normal renal function implied) **Clinical Pearl:** D-dimer elevation confirms thrombosis but is not specific; compression ultrasound is the gold standard for DVT diagnosis. Once confirmed, anticoagulation should not be delayed. **Warning:** Do not confuse **thrombolysis** (catheter-directed or systemic) with **anticoagulation**. Thrombolysis is reserved for: - Massive PE with hemodynamic instability - Acute limb ischemia from arterial thrombosis - Upper extremity DVT with severe symptoms (rare) Routine proximal DVT is managed with anticoagulation alone. **Mnemonic: LMWH vs UFH — "LMWH Loves Outpatients"** - **L**MWH: Predictable, SC, outpatient-friendly - **U**FH: Needs IV, ICU, aPTT monitoring, but reversible