Superficial Vein Thrombosis (SVT) Treated With Rivaroxaban Versus Fondaparinux

Inclusion Criteria: * acute symptomatic supragenual superficial vein thrombosis of the leg * at least one of the following major risk factor for VTE: * age \> 65 years or * male sex or * history of DVT/PE/SVT or * history of cancer or active cancer or * autoimmune disease or * SVT of a non-varicose vein * thrombus extension of at least 5 cm * proximal thrombus end with more than 3 cm distance to the saphenofemoral junction (SFJ) * age \> 18 years * written informed consent Exclusion Criteria: * other indication for therapeutic anticoagulation such as acute deep vein thrombosis, acute pulmonary embolism, atrial fibrillation with indication for anticoagulant therapy * any PE or DVT within last 6 months before inclusion * clinical signs of PE without objective exclusion (CT or VQ scan, angiography) * SVT without signs of thrombotic/inflammatory activity (activity signs: diameter \> 4 mm, pain, redness, elevated local or systemic temperature) * SVT after sclerotherapy * Duration of symptoms \> 3 weeks * pretreatment of more than 72 h with therapeutic dosages of oral or parenteral anticoagulants * pretreatment of more than 5 days with subtherapeutic oral or parenteral anticoagulants * indication for escalated antiplatelet therapy (monotherapy with aspirin \> 325 g/d and any dual antiplatelet therapy) * SVT closer than 3 cm to saphenofemoral junction (SVJ) * anticipated superficial vein surgery within 90 days * anticipated thrombolytic therapy within 90 days * manifest clinically relevant bleeding * clinically relevant bleeding in the last 30 days before study inclusion * major surgery within last 30 days before inclusion * ophthalmic, spinal or cerebral surgery within last 90 days * severe head trauma within last 90 days * hemorrhagic stroke within last 12 months * hereditary or acquired severe hemorrhagic diathesis * gastrointestinal bleeding within last 90 days requiring endoscopy * uncontrolled arterial hypertension (systolic \> 180 mm Hg, diastolic \> 110 mm Hg) * acute endocarditis * low platelet count (\< 100 x 109/l) * Prothrombin time \< 50 % * calculated creatinine clearance \< 30 ml/min * significant liver disease such as acute hepatitis, chronic active hepatitis, cirrhosis * life expectancy \< 3 months * any contraindications listed for rivaroxaban or fondaparinux * women of child bearing potential without safe contraception method * pregnant or breastfeeding women * participation in another trial with pharmacological intervention