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Deep Vein Thrombosis (DVT): Risk Factors, Prevention & When to Act

Deep Vein Thrombosis (DVT) is a blood clot in a deep vein, usually the leg (calf, thigh, pelvis). It affects ~1–2 per 1,000 adults annually. The danger: clot can embolize to lungs → Pulmonary Embolism (PE), a life-threatening emergency.

Major Risk Factors (Virchow's Triad: Stasis, Hypercoagulability, Endothelial Injury)

CategorySpecific FactorsRelative Risk
ImmobilityLong travel (>4h), hospitalization, surgery (esp. orthopedic/abdominal/pelvic), paralysis, casting↑↑↑
Age>60 years (exponential increase)↑↑
Surgery/TraumaMajor surgery (esp. hip/knee replacement, cancer surgery), fractures↑↑↑ (without prophylaxis)
CancerActive malignancy (pancreas, lung, brain, stomach, ovarian), chemotherapy↑↑↑ (4–7x baseline)
HormonalCombined OCP/HRT (estrogen), Pregnancy (5–10x), Postpartum (6wks)↑↑ (estrogen); ↑↑↑ (pregnancy)
Genetic/HereditaryFactor V Leiden, Prothrombin G20210A, Protein C/S deficiency, Antithrombin deficiencyVariable (heterozygous 3–8x; homozygous 80x)
Medical ConditionsHeart failure, COPD, IBD (flare), Nephrotic syndrome, SLE, Antiphospholipid syndrome↑↑
ObesityBMI >30 (2–3x risk)↑↑
SmokingCurrent/former↑
Prior VTEPrevious DVT/PE (recurrence risk ~30% at 10yr)↑↑↑
Varicose VeinsSuperficial venous insufficiency↑

Symptoms (Often Unilateral)

  • Calf/thigh pain, tenderness (often deep, worse with dorsiflexion – Homans' sign unreliable)
  • Swelling (circumference difference >2–3 cm vs. other leg)
  • Warmth, erythema, superficial vein distension
  • Asymptomatic in ~50% – high index of suspicion needed.

Diagnosis

  1. Wells Score (clinical probability) → guides testing.
  2. D-dimer: High sensitivity, low specificity. Negative rules out DVT in low/probability.
  3. Compression Ultrasound (CUS): Gold standard (non-compressible vein = DVT).
  4. CT/MR Venography for pelvic/IVC clots.

Prevention (Evidence-Based)

  • Hospitalized/Surgical: Pharmacologic (LMWH, Fondaparinux, DOAC) + Mechanical (IPC, GCS) per protocol.
  • Long Travel: Aisle seat, hourly ambulation, calf exercises, hydration, avoid alcohol/sedatives. Consider below-knee GCS (15–30 mmHg) if risk factors. No routine anticoagulation for healthy travelers.
  • Pregnancy/Postpartum: Risk assessment → prophylactic LMWH if high risk.
  • Cancer: Primary prophylaxis in high-risk ambulatory (Khorana score ≥2) – DOAC/LMWH.
  • Lifestyle: Weight management, smoking cessation, regular activity, hydration.

When to Seek Emergency Care

  • Sudden dyspnea, pleuritic chest pain, tachycardia, hemoptysis, syncope → suspect PE, call 911.
  • Acute leg swelling/pain → same-day ultrasound.

DVT is preventable and treatable. Know your risks. Advocate for prophylaxis during hospitalization/surgery. Act fast on symptoms.

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