Diagnosis of deep venous thrombosis: accuracy of colour doppler ultrasound compared with venography.

Doppler ultrasound is becoming increasingly accepted as an accurate, non-invasive means of imaging in suspected deep venous thrombosis (DVT). Several studies done abroad have reported (combined) sensitivity of 95% and specificity of 98%. Locally, however, we have still been relying primarily on venography to diagnose lower limb DVT. We performed a prospective study to assess the accuracy of ultrasound compared to venography, in the local context. Forty-one limbs were studied by ultrasound within 24 hours of a venogram examination. We assessed grey-scale appearance, compressibility, presence or absence of flow, and flow characteristics. Seventeen venograms were positive for DVT, and ultrasound was positive in all seventeen cases. There were two false positive ultrasound examinations. Two cases of small localised thrombi in the superficial femoral vein only were accurately detected by ultrasound. One case of isolated calf thrombosis was also successfully diagnosed. Overall, sensitivity and specificity for detection of lower limb DVT was 100% and 91.7% respectively. Overall accuracy was 95.1%.