Clinical relevance of distal deep vein thrombosis. Review of literature data.

The standard diagnostic approach of suspected deep vein thrombosis (DVT) is serial lower limb compression ultrasound (CUS) of proximal veins. Although it only assesses the proximal veins, withholding anticoagulant treatment in patients with a negative CUS on day one and after one week has been proven to be safe. However, in many centres, distal DVT is systematically screened for and treated by anticoagulants. The objectives of the review were 1) to evaluate the rate of extension of distal DVTs to proximal veins 2) to compare the safety of proximal limited CUS versus single complete CUS. We performed a MEDLINE search covering the period from January 1983 to January 2005 by using the key-words "calf vein thrombosis", "distal thrombosis" and "compression ultrasonography". English, German and French language original studies were retrieved. Moreover, references of retrieved articles were screened in order to detect missed pertinent articles. We pooled data of management studies where proximal or complete (i.e. proximal and distal) CUS were used, respectively. Studies evaluating CUS limited to the proximal veins showed a good safety profile with a pooled estimate of the 3-month thromboembolic rate of 0.6% (95% CI: 0.4-0.9%) in patients in whom anticoagulation was withheld. Studies using proximal and distal CUS showed a similar pooled estimate of the 3-month thromboembolic rate (0.4%, 95% CI: 0.1-0.6%) but distal DVT accounted for as many as 50% of all diagnosed DVTs in those series. Therefore, searching for distal DVT potentially doubles the number of patients given anticoagulant therapy and entails a risk of over-treatment. Data suggesting that anticoagulation is indicated for distal DVT are limited, and realizing distal CUS entails a risk of over-treatment. There is an urgent need for randomised trials assessing the usefulness of anticoagulant treatment in distal DVT.