A 48-year-old woman is admitted with acute deep vein thrombosis. Duplex ultrasonography confirms thrombosis in the lower limb. Which is the most common site of DVT in the lower extremity?

Explanation

## Sites of Deep Vein Thrombosis in the Lower Limb **Key Point:** The femoral vein is the most common site of DVT in the lower extremity, followed by the popliteal vein. Calf veins (tibial and peroneal) are less commonly involved. ### Frequency of DVT by Site | Vein | Frequency | Clinical Significance | |------|-----------|----------------------| | **Femoral vein** | 40–50% | Most common; high risk of PE | | **Popliteal vein** | 25–35% | Second most common; significant PE risk | | **Iliac vein** | 10–15% | Often associated with femoral DVT | | **Calf veins (tibial/peroneal)** | 15–25% | Lower PE risk; may be proximal extension | ### Anatomical Basis The femoral vein is the largest and most dependent vessel in the lower limb, making it: - A site of relative venous stasis - Susceptible to endothelial injury from trauma or catheterization - A common location for thrombus formation in immobilized patients **High-Yield:** Proximal DVT (femoral and popliteal veins) carries a 40–50% risk of pulmonary embolism if untreated, whereas isolated calf DVT has a 5–10% PE risk. **Clinical Pearl:** The femoral vein is commonly affected in post-operative patients, those with prolonged immobilization, and patients with malignancy or hypercoagulable states. **Mnemonic:** **FPI** — Femoral > Popliteal > Iliac (in frequency of DVT).