22.22: Venous Thrombosis II: Clinical Manifestations and Diagnostic Studies

The key difference between Superficial Vein Thrombosis (SVT) and Deep Vein Thrombosis (DVT) lies in their location and severity.

Clinical Manifestations

SVT typically presents with localized pain, tenderness, and redness along the course of a superficial vein, often accompanied by a palpable, cord-like structure under the skin. This condition is usually less dangerous than DVT but can be uncomfortable and may lead to complications such as cellulitis or, rarely, a clot extension into the deep venous system.

DVT, on the other hand, occurs in the deeper veins, most commonly in the legs. Clinical manifestations of DVT include unilateral leg edema, pain, tenderness upon palpation, dilated superficial veins, a sense of fullness in the calf or thigh, warm skin, paresthesias, redness, and a systemic temperature above 100.4°F. If the inferior vena cava is involved, both legs may become edematous and cyanotic. Involvement of the superior vena cava can cause similar symptoms in the arms, neck, back, and face. DVT is more concerning than SVT due to its potential to cause life-threatening complications such as pulmonary embolism (PE). In PE, a clot dislodges and travels to the lungs, causing respiratory distress or sudden death.

Assessment and Diagnostic Findings

Assessment and diagnostic findings for DVT and SVT involve clinical evaluation, laboratory tests, and imaging studies. Clinically, SVT presents with localized tenderness, redness, and a palpable cord-like structure along the superficial vein. DVT is characterized by unilateral leg swelling, pain, warmth, and redness.

Laboratory tests include measuring activated partial thromboplastin time (aPTT), activated clotting time (ACT), international normalized ratio (INR), bleeding time, hemoglobin (Hgb), hematocrit (Hct), and platelet count, which may be altered in patients with blood disorders. Elevated D-dimer levels, indicating fibrin degradation, suggest venous thromboembolism (VTE), with normal levels less than 250 ng/mL. The presence of fibrin monomer complexes, indicative of thrombus formation, also suggests VTE, with normal levels being less than 6.1 mg/L.

Noninvasive imaging studies, such as duplex ultrasound and venous compression ultrasound, are commonly used. Duplex ultrasound combines compression with spectral and color Doppler to evaluate vein compressibility and intraluminal filling defects. In a normal finding, veins collapse with external pressure; failure to collapse suggests a thrombus.

Invasive studies include computed tomography venography (CTV), which uses spiral CT with contrast injection to evaluate veins in the pelvis, thighs, and calves and can be combined with CT angiography for VTE evaluation. Magnetic resonance venography (MRV) uses MRI to evaluate blood flow through veins. It is highly accurate for pelvic and proximal veins but less for calf veins; it can also distinguish between acute and chronic thrombi.

Conclusion

Accurate assessment and diagnosis of SVT and DVT are crucial for guiding appropriate treatment and preventing complications like pulmonary embolism in DVT.