The diagnosis of recurrent deep venous thrombosis

Duplex ultrasound is the preferred investigation for the diagnosis of initial and recurrent deep venous thrombosis. The contralateral leg should be scanned when thrombosis is diagnosed as it is bilateral in 30% of cases. At the completion of anticoagulant therapy a venous duplex scan should be performed to establish a new baseline. Recurrent deep venous thrombosis can subsequently be diagnosed if there is a 5 cm increase in the extent of residual thrombus or an increase in the compressed thrombus diameter of more than 2 mm. If there is any doubt about the presence of a recurrent thrombosis serial ultrasound should be used.