Hematology · Venous Thromboembolism
The facts most likely to be tested
Virchow's triad—stasis, hypercoagulability, and endothelial injury—represents the fundamental pathophysiology of deep vein thrombosis.
The Wells criteria is the validated clinical decision rule used to determine the pretest probability of DVT before ordering diagnostic imaging.
Compression ultrasonography with Doppler is the first-line diagnostic test for suspected lower extremity DVT due to its high sensitivity and specificity.
D-dimer testing is highly sensitive and is used to rule out DVT in patients with low or intermediate pretest probability.
Homan's sign—calf pain upon passive dorsiflexion of the foot—is a classic but non-specific physical exam finding that lacks diagnostic utility.
Anticoagulation with low-molecular-weight heparin (LMWH) or direct oral anticoagulants (DOACs) is the standard of care for acute DVT management.
An inferior vena cava (IVC) filter is indicated only in patients with an acute proximal DVT who have an absolute contraindication to therapeutic anticoagulation.
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A 58-year-old male presents to the emergency department with three days of unilateral left lower extremity swelling and dull aching pain. He recently completed a 12-hour international flight. Physical examination reveals pitting edema, erythema, and tenderness to palpation along the deep venous system of the left calf. His heart rate is 92 bpm, and his oxygen saturation is 98% on room air. A Wells score is calculated, placing him in the high-probability category.
What is the most appropriate next step in the management of this patient?
Compression ultrasonography of the lower extremity
The patient has a high pretest probability for DVT based on the Wells criteria, necessitating immediate diagnostic imaging with compression ultrasonography rather than D-dimer testing.
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High yield triage
Etiology / Epidemiology
Driven by Virchow's triad: stasis, endothelial injury, and hypercoagulability. High risk in post-op, malignancy, and OCP use.
Clinical Manifestations
Presents with unilateral leg swelling, warmth, and tenderness. Homan's sign is classic but low sensitivity.
Diagnosis
Venous duplex ultrasound is the diagnostic test of choice. Use D-dimer to rule out in low-probability patients.
Treatment
Low molecular weight heparin (LMWH) or DOACs (e.g., apixaban) are first-line. Avoid warfarin monotherapy due to initial protein C depletion.
Prognosis
Primary concern is pulmonary embolism (PE). Long-term risk includes post-thrombotic syndrome.
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Epidemiology & Etiology
Incidence increases with age and presence of Virchow's triad. Major risk factors include prolonged immobilization, orthopedic surgery, malignancy, and Factor V Leiden mutation. Oral contraceptives and pregnancy significantly elevate risk in younger females.
Pertinent Anatomy
Thrombi most commonly originate in the calf veins (popliteal, tibial) and propagate proximally. Involvement of the iliofemoral segment carries the highest risk for massive embolization.
Pathophysiology
Thrombus formation occurs when procoagulant factors overwhelm natural anticoagulants. Stasis allows activated clotting factors to accumulate, while endothelial damage exposes subendothelial collagen, triggering the coagulation cascade.
Clinical Manifestations
Patients present with unilateral extremity edema, erythema, and calf pain. Homan's sign (pain with dorsiflexion) is historically cited but clinically unreliable. Sudden onset dyspnea or pleuritic chest pain suggests secondary pulmonary embolism.
Diagnosis
Calculate Wells criteria to determine pre-test probability. In low-risk patients, a negative D-dimer effectively rules out DVT. Venous duplex ultrasound is the gold standard for confirmation, demonstrating non-compressibility of the vein.
Treatment
Initiate anticoagulation immediately with LMWH or DOACs (e.g., apixaban or rivaroxaban). Contraindications include active major bleeding or severe thrombocytopenia. If anticoagulation is contraindicated, place an inferior vena cava (IVC) filter.
Prognosis
Immediate mortality is linked to pulmonary embolism. Chronic complications include post-thrombotic syndrome (venous stasis ulcers, chronic pain) and venous claudication.
Differential Diagnosis
Cellulitis: presents with fever and diffuse skin involvement
Baker's cyst: rupture mimics DVT but shows posterior knee mass
Muscle strain: history of acute trauma or exertion
Lymphedema: chronic, non-pitting, bilateral progression
Superficial thrombophlebitis: palpable cord along superficial vein