Limited Versus Extended Ultrasonography for the Diagnosis of Clinically Symptomatic Deep Vein Thrombosis of the Lower Extremities. A Randomized Study

All consecutive outpatients referred to the study center with clinically suspected deep vein thrombosis are potentially eligible for inclusion. Patients are excluded if they have a history of previous venous thromboembolism, have clinical suspicion of pulmonary embolism, have a life expectancy shorter than 3 months, have used therapeutic doses of unfractionated heparin, low molecular weight heparin or oral anticoagulants for more than 48 hours, have another indication for anticoagulant treatment, are pregnant, are aged less than 18 years, are inaccessible to follow-up, or refuse participation in the study.

Randomization Before randomization, patients are interviewed using a standardized questionnaire in order to collect information on risk factors for venous thrombosis, and the presence of several clinical signs and symptoms. Subsequently, they are randomized to the limited or the extended ultrasound strategy through computer generated lists, each of 100 patients arranged in balanced blocks of 10, specific for each center. The list is accessible only for a study nurse who informed the study physicians about group allocation once patients had provided informed consent.

Initial diagnostic workup Patients randomized to limited ultrasonography undergo compression ultrasonography, confining the investigation to the common femoral and the popliteal vein down to its trifurcation. In patients with normal findings D-dimer testing is performed, and they are subsequently managed according to its results: patients with normal D-dimer levels do not receive further investigation, while those with abnormal test are scheduled for repeat compression ultrasonography within one week.

Patients randomized to the extended ultrasonography receive first the evaluation of the proximal vein system, including the common femoral, the superficial femoral and the popliteal vein down its trifurcation. Then patients with compressible proximal veins undergo the extensive evaluation of the calf vein system, including the anterior tibial, posterior tibial and peroneal veins, and, if the deep veins were normal, also of the muscular (gastrocnemial and soleal) veins.

Limited ultrasonography and D-dimer The common femoral at the groin, and the popliteal vein down to its branching into the calf deep veins at the popliteal fossa, are examined in the transverse plane only, with a 7.5 MHz linear probe. The test results are categorized as normal (compressible veins) or abnormal (non compressible veins).