This patient should undergo venous duplex ultrasonography of the left thigh to evaluate for deep venous thrombosis (DVT) associated with his superficial venous thrombophlebitis (SVT). DVT or pulmonary embolism (PE) develops in up to 3.3% of patients with isolated SVT. The risk increases in patients with SVT of the great or small saphenous vein, with extremity swelling more pronounced than would be expected from the SVT alone, and with progressive symptoms. In these situations, such as with this patient, duplex ultrasonography is indicated to assess for the possibility of an associated DVT.

The effectiveness of low-dose aspirin to treat or prevent propagation of clots in SVT has not been established. Additionally, the use of other anticoagulants for treatment of SVT is controversial. Some evidence indicates that patients with extensive SVT may benefit from a short course of anticoagulant therapy. However, because of a lack of additional data, the specific patients for whom treatment is indicated, the optimal duration of anticoagulation, and the appropriate drug dose and choice are unknown.

D-dimer testing has no utility for differentiating superficial from deep venous thrombosis because levels may be elevated in both conditions. It would, therefore, not be useful in this patient.

Nonextensive SVT, defined as less than 5 cm in length and not near the deep venous system, may be treated with only symptomatic therapy consisting of analgesics, anti-inflammatory medications, and warm or cold compresses for symptom relief, because the risk of progression into the deep venous system and of PE is low.