deep vein thrombosis
Summary
Deep vein thrombosis (DVT) is the formation of a blood clot within a deep vein, most commonly in the lower extremities (femoral, popliteal, or iliac veins). It classically presents with unilateral leg swelling, warmth, erythema, and pain, and is a major risk factor for pulmonary embolism (PE). Risk factors are captured by Virchow's triad: stasis, endothelial injury, and hypercoagulability.
Detail
Pathophysiology: DVT arises from Virchow's triad—venous stasis (immobility, long travel, CHF), endothelial injury (trauma, surgery, IV catheters), and hypercoagulability (malignancy, pregnancy, OCPs/HRT, inherited thrombophilias like Factor V Leiden, protein C/S deficiency, antithrombin III deficiency, antiphospholipid syndrome). Clots typically form in the valve pockets of deep veins where flow is sluggish, then propagate proximally.
Clinical presentation: unilateral leg swelling, warmth, tenderness, erythema, and a palpable cord; Homan's sign (calf pain on dorsiflexion) is neither sensitive nor specific and is not used clinically. Many DVTs are asymptomatic until embolization occurs.
Diagnosis: Wells score to stratify pretest probability; D-dimer (high sensitivity, low specificity) to rule out DVT in low-probability patients; compression ultrasonography with Doppler is the gold standard imaging test (loss of vein compressibility indicates thrombus). Venography is rarely used now.
Complications: Pulmonary embolism (clot embolizes to pulmonary arteries, causing hypoxia, pleuritic chest pain, tachycardia, and potentially sudden death from saddle embolus); post-thrombotic syndrome (chronic venous insufficiency, edema, skin changes, ulceration) due to valve damage; phlegmasia cerulea dolens in severe cases.
Treatment: Anticoagulation is mainstay—heparin (unfractionated or LMWH) bridging to warfarin, or direct oral anticoagulants (DOACs like rivaroxaban, apixaban) which are now first-line for most patients. Duration depends on provoked vs. unprovoked status (3 months vs. indefinite). IVC filter is used if anticoagulation is contraindicated. Thrombolysis or thrombectomy considered in massive/limb-threatening DVT.
High-yield associations: Factor V Leiden (most common inherited hypercoagulable state, resistance to activated protein C), malignancy (Trousseau syndrome), long-haul travel, surgery (especially orthopedic), pregnancy, nephrotic syndrome (loss of antithrombin III), and paroxysmal nocturnal hemoglobinuria.
Sources
- First Aid for the USMLE Step 1
- Pathoma - Fundamentals of Pathology (Husain)
- UpToDate: Diagnosis of suspected deep vein thrombosis
- Harrison's Principles of Internal Medicine
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