Duplex ultrasound diagnosis of lower limb deep venous thrombosis

To compare a non-invasive technique with contrast venography in the diagnosis of lower limb deep venous thrombosis (DVT), 355 patients (380 limbs) were examined over 15 months, using Duplex ultrasound. During this period, ascending venograms were performed in 53 of these patients (56 limbs) and the results were compared. Duplex detection of intraluminal thrombus was based on venous compressibility, Doppler-derived flow spectra, and visualization of thrombus within the lumen. Venography was designated the 'gold standard'. Duplex scanning had a sensitivity of 90.9%, and specificity of 91.3% in diagnosing DVT anywhere in the lower limb. Sensitivity, specificity, and accuracy were best in the femoral segment (95.2%, 100%, 98.2%, respectively), and fell slightly in the more distal limb: popliteal segment (90.4%, 97.1% and 94.6%), and calf veins (88.8%, 92.0% and 90.4%). These results indicate that duplex scanning produces sufficiently accurate data in the diagnosis of lower limb DVT to warrant its clinical use. It provides both the facility for diagnosis without the risks of contrast venography, and permits repeated imaging to follow the immediate progression of disease and efficacy of treatment.