DISCREPANCIES BETWEEN VENOGRAPHY AND REAL TIME B MODE ULTRASOUND IMAGING IN THE DIAGNOSIS OF DEEP VEIN THROMBOSIS

Methods : in this prospective study, real time B Mode ultrasound imaging (USI) was compared to bilateral ascending contrast venography, double blindly, in 430 patients suspected of deep vein thrombosis (DVT) or pulmonary embolism.

A complete scan of the venous system from the inferior vena cava to the calf veins, was performed with a high resolution duplex system (DIASONICS DRF 400) and coupled systematically with a C.W. Doppler examination. The results obtained by USI were thus compared to the venograms performed on a total of 854 legs.

Results : there are corresponding results in 95% of the legs (808/854). If we consider venography as the standard of reference, the sensitivity of USI is 98% (325/333) and the specificity 94% (483/514). Isolated calf vein thrombosis are detected in 91% (84/92) of the legs and proximal DVT in 100% (241/241) in this series whatever the topography and the extension of the thrombosis and whatever the degree of the obstruction of the vein.

Discrepancies found in 46 legs are related to :

- 8 DVT located in the calf (6 in the presumed healthy leg) diagnosed only by venography.

- 27 DVT (18 distal, 9 femoral or iliac) detected only by USI

- 9 doubtful examinations with USI not confirmed by venography

- 2 doubtful venograms with negative USI test.

Comments : Calf vein thrombosis especially located in the soleal sinuses and the gastrocnemius with in most cases the direct image of the thrombus are more often detected by USI provided that the technique and the equipment are appropriate.

The absence of visualisation of venous segments with venography is not specific of venous thrombosis. These veins non affected by the thrombosis are not filled by the contrast medium when located above in occluded ilio-femoral or ilio-caval junction or when they are the site of extrinsic compression. The direct image of the vein and the surrounding structures obtained with USI enhances the diagnostic sensitivity and specificity and provides precision of the exact extension of the thrombosis.

Due to these differences, can venography still be considered as the standard of reference in the diagnosis of DVT and their precise localisation ?