A 49-year-old man returns from a 1-week trip to Hong Kong and reports right calf cramping that started after picking up his luggage. Over the next 2 days the cramping persists, is made worse by walking, and the right calf becomes swollen (Figure 52-1). He sees his primary care physician, who refers the patient for a lower extremity duplex ultrasound examination. The examination reveals no evidence for proximal deep vein involvement, but he does have acute peroneal and posterior tibial vein thrombosis. Low–molecular weight heparin therapy is initiated and the patient is transitioned to warfarin anticoagulation for a 3-month therapeutic course.