DIAGNOSTIC UTILITY OF COLOR DOPPLER ULTRASOUND IN LOWER-LIMB DEEP-VEIN THROMBOSIS IN PATIENTS WITH CLINICAL SUSPICION OF PULMONARY THROMBOEMBOLISM

The diagnosis of pulmonary thromboembolism is frequently based on vent ilation-perfusion scintigraphy and ascending lower limb venography whe n pulmonary angiography is not available. The aim of this study is to compare color Doppler ultrasound against ascending venography in the e valuation of the lower limb deep vein system in patients with clinical suspicion of pulmonary embolism, with special attention to calf veins . We prospectively studied 30 patients with clinical suspicion of pulm onary embolism in whom a color Doppler ultrasound and venogram were pe rformed with no more than a 3-h interval between both procedures. The diagnostic criteria was that of loss of venous compressibility. The 'c olor' ability was used to identify artery from vein. Out of 15 patient s in whom a venogram proved positive (50%), 9 had isolated calf vein t hrombosis (60%). In 5 patients, the color Doppler ultrasound of the ca lf was considered inconclusive. Overall sensitivity was 53%, specifici ty 100%, positive predictive value 100%, and negative predictive value 68%. In the femoropopliteal system, sensitivity was 83% and specifici ty 100%. Considering all patients, sensitivity in the calf system was 40%. Excluding the 5 patients who were difficult to assess, sensitivit y increased to 60%. In conclusion, color Doppler ultrasound is not as sensitive as venography in dealing with patients with clinical suspici on of pulmonary embolism, due to its low sensitivity in the calf syste m when distal thrombi need to be excluded. However, a reasonable alter native is to begin by performing a compression ultrasonography of the femoropopliteal system. Color Doppler ultrasonography of the calf syst em represents a rarely sensitive and arduous task and does not seem ju stifiable in this type of patient. Even if deep calf veins are examine d, a negative sonogram does not exclude thrombi in this region and ven ography should be performed if the clinician needs to prove their abse nce.