Compression ultrasonography for diagnosing deep vein thrombosis

Editor—We advise caution in adopting the proposed abbreviated examination protocol for detecting deep vein thrombosis in the leg.1,2 Our experience using duplex ultrasonography to study the natural course of deep vein thrombosis leads us to make the following points. Firstly, it is incorrect that calf deep vein thrombosis cannot be accurately diagnosed by duplex ultrasonography. Many reports from expert centres refute such an opinion, although we agree that the skill and experience of the sonographer is important. Secondly, about 14% of isolated calf deep vein thromboses propagate into the proximal veins. Others have reported an incidence of up to 20% propagation.3 Thirdly, because of the varying attitudes to management of isolated calf deep vein thrombosis some will argue against the need to investigate these veins on the basis that pharmacological treatment is not contemplated. Fourthly, isolated superficial femoral deep vein thrombosis without involvement of the popliteal (distal) or common femoral (proximal) venous segments can occur. This presentation may cause few clinical signs and symptoms, and the thrombus only partially occludes the vein with poor adhesion of the clot to the vein wall. The frequency of this presentation makes it mandatory to examine the whole length of the veins in the thigh. The additional time required is minimal, but the information obtained is important. Fifthly, the editorial scenario of office based worldwide facilities to diagnose deep vein thrombosis accurately2 requires sufficient technical skill and experience with audit control to assure standards at each of these offices. Reports of therapeutic results could otherwise be confusing. The examination protocol recommended by Cogo et al has the attraction of saving time but does so at the expense of ignoring 15-25 cm of vein in the thigh (which might take 2 minutes to examine) and excluding the calf veins, which have a potential to propagate thrombi in 14-20% of cases. Re-investigation after a week detected a further 1% of deep vein thromboses in those venous segments being examined. We believe that one full examination of the veins of the leg would provide more comprehensive information, take less time, and be more cost effective than investing in two examinations over a week evaluating only short selected segments of the venous system.