Deep Vein Thrombosis
Hematology / Vascular Medicine
Illness script · Hematology / Vascular Medicine
Deep Vein Thrombosis
Thrombus formation in a deep vein (most often proximal lower extremity) causing obstruction and risk of pulmonary embolism.
This illness script for Deep Vein Thrombosis covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Virchow's triad: stasis, hypercoagulability, endothelial injury
- Prolonged immobility (long flights, hospitalization, post-op)
- Malignancy — especially pancreatic, lung, GI cancers
- Inherited thrombophilia: Factor V Leiden (most common), Prothrombin G20210A, Protein C/S deficiency
- OCP/HRT, pregnancy, postpartum period
- Prior DVT/PE; obesity; advanced age
02
Presentation
- Unilateral calf/thigh pain, swelling, erythema, warmth — asymmetry is key
- Homans' sign (calf pain on dorsiflexion) — insensitive/nonspecific, historically taught
- Pitting edema and venous distension of affected extremity
- Phlegmasia cerulea dolens: massive ilio-femoral DVT → limb cyanosis, ischemia (rare emergency)
- Many DVTs are asymptomatic; found incidentally on imaging
03
Pathophysiology
- Stasis reduces flow → activated clotting factors accumulate → thrombus propagates
- Endothelial damage exposes tissue factor → extrinsic coagulation cascade activation
- Proximal clot (iliac, femoral, popliteal) carries highest risk of PE embolization
- Chronic valvular destruction → post-thrombotic syndrome (chronic venous insufficiency)
04
Diagnostics
- Pre-test probability: Wells DVT score (low/moderate/high) guides workup
- D-dimer ELISA: high sensitivity; excellent to rule OUT when Wells score low (NPV ~99%)
- Compression ultrasonography: first-line imaging — noncompressibility of vein = diagnostic
- CT venography or MRI venography for pelvic/IVC thrombosis not seen on US
- Thrombophilia workup: defer until off anticoagulation and acute phase resolved
05
Management
- Anticoagulation is mainstay: DOAC (rivaroxaban or apixaban) first-line for most patients
- LMWH bridge → warfarin (INR 2–3) if DOAC contraindicated (e.g., severe renal impairment)
- Duration: provoked DVT 3 months; unprovoked or cancer-associated consider indefinite
- LMWH preferred in active malignancy (or DOAC — apixaban/rivaroxaban also acceptable)
- Catheter-directed thrombolysis or thrombectomy for massive ilio-femoral DVT with limb ischemia
- IVC filter: only if anticoagulation absolutely contraindicated (not a routine adjunct)
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Cellulitis
Cellulitis has erythema tracking with systemic signs (fever); compression US normal (vein compressible)
Ruptured Baker's Cyst
Posterior knee mass history; no clot on US; crescent sign on MRI; no anticoagulation needed
Pulmonary Embolism
DVT source vs. PE consequence — PE presents with dyspnea/hypoxia/pleuritic chest pain, not just limb swelling
Superficial Thrombophlebitis
Palpable cord in superficial vein, minimal swelling; US confirms no deep involvement; NSAIDs often sufficient
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.