Marc Righini

Summary: Isolated distal deep vein thrombosis (DVT) represents up to 50% of all lower limb DVT in ultrasound series and is a frequent medical condition, which management is not well established. Data arising from registries and non-randomized studies suggest that most distal DVTs do not extend to the proximal veins and have an uneventful follow-up when left untreated. This data had some impact on international recommendations like the American College of Chest Physicians (ACCP), whose last version stated that ultrasound surveillance might be an option for selected low-risk patients. However, robust data arising from randomized studies are scarce. Indeed, only seven randomized trials assessing the need for anticoagulation for calf DVT have been published. Many of these trials had an open-label design and were affected by methodological limitations. When considering randomized placebo-controlled trials, one included low-risk patients and was hampered by a limited statistical power (CACTUS study). Nevertheless, data from this trial tend to confirm that the use of therapeutic anticoagulation in low-risk patients with symptomatic calf DVT is not superior to placebo in reducing VTE but is associated with a higher risk of bleeding. A second randomized placebo-controlled trial did not assess the necessity of anticoagulant treatment but rather the long-term risk of recurrence and compared 6 weeks versus 12 weeks of treatment with rivaroxaban (RIDTS study). Finally, the last available randomized trial compared a 3-month versus a 12-month edoxaban treatment in patients with cancer and mainly asymptomatic distal DVT, detected by systematic compression ultrasonography. Overall, available data suggest that the use of therapeutic anticoagulation in low-risk patients with symptomatic calf DVT is not superior to placebo in reducing VTE. High risk patients (previous VTE, active cancer, inpatients) might benefit from a course of anticoagulant treatment. However, the optimal anticoagulant intensity and duration are uncertain and further studies are needed.