Anticoagulant treatment for isolated distal deep vein thrombosis: a systematic review and meta-analysis.

The optimal management of isolated distal deep vein thrombosis (IDDVT) is uncertain. To assess the efficacy and safety of anticoagulation in patients with IDDVT we performed a systematic review and meta-analysis of randomized and cohort studies on anticoagulation for IDDVT. Efficacy outcomes included recurrent deep vein thrombosis (DVT), pulmonary embolism (PE), proximal progression of IDDVT, post-thrombotic syndrome (PTS). Safety outcomes included major bleeding and clinically relevant non-major bleeding (CRNMB). Pooled incidence and risk ratios (RR) with 95% confidence intervals (CI) were calculated. Treatment duration was defined as short (<6 weeks), long (6-12 weeks), or extended (>12 weeks). Fifty-three studies (14,580 patients) were included. The incidence of recurrent DVT and proximal progression was 16% and 11% in untreated patients, 7% and 7% in short, 6% and 3% in long, and 4% and 2% in extended anticoagulation, respectively. The incidence of PE (2%) and major bleeding (2%) was low, with similar risk across groups of treatment duration. The incidence of PTS was 30% in untreated patients, 11% in short, and 0% in long anticoagulation. The incidence of CRNMB was respectively 2%, 1%, 4%, and 8%. Patients receiving short courses of anticoagulation had higher risk of recurrent VTE (RR=2.72; 95% CI: 1.19-6.23) and proximal progression (RR=3.86; 95% CI: 1.77-8.43) than patients receiving long anticoagulation, with similar bleeding risk in patients with IDDVT, anticoagulation seemed associated with lower risk of recurrent VTE and proximal progression, and similar bleeding risk compared to no anticoagulant treatment. Long-term treatment duration appeared to be more effective.