Floating thrombi: diagnosis and follow-up by duplex ultrasound.

The clinical features and evolution of floating thrombi (FT) diagnosed by duplex ultrasound were examined. In 76 consecutively diagnosed above-knee deep venous thromboses the prevalence of FT was 18%. Of 44 FT diagnosed in 39 patients, 18 (39%) were located in the common femoral, 12 (26%) in the popliteal and seven (15%) in the external iliac veins. Serial duplex examinations revealed that 31% of FT in the iliofemoral segment disappeared 33% remained unchanged and 36% adhered to the vein wall within 2 weeks following diagnosis. After 3 months, 87% of the floating segments had disappeared, irrespective of the localization or therapeutic regimen. Thirteen patients experienced pulmonary embolism before (12/13) or following (4/13) diagnosis of floating thrombosis; three of four superficial femoral vein FT embolized. Fifteen per cent of the patients with FT died during the study period and 28% of the thrombi were associated with a malignant neoplasm; the incidence of malignancy was 60% in superficial and 39% in common femoral vein FT.