Risk factors for delayed recanalization of calf vein thrombosis

PURPOSE To determine the risk factors of delayed recanalization of isolated calf vein thrombosis (CVT). METHODS One hundred fifty limbs of 110 patients with CVT between September 2007 and April 2010 were enrolled. We used ultrasonography for the diagnosis and follow-up examinations of CVT. We calculated recanalization rates at 1 and 3 months after initial diagnosis and analyzed the risk factors associated with delayed recanalization of CVT. RESULTS CVTs were located in the muscular calf vein in 110 (73.3%), in the deep calf vein in 18 (12%), and in both in 22 cases (14.7%). Among all CVTs, 94 limbs (63%) were symptomatic. Major risk factors for CVT were orthopedic surgery (87.3%), malignancy (21.3%), and immobilization (15.3%). Sixty-seven patients (60.9%) were treated with oral anticoagulation therapy, while 43 patients by low molecular weight heparin (n = 19) or by conservative methods including elastic compression stockings and ambulation (n = 21). The cumulative recanalization rate at 1 and 3 months was 23% and 82% and it was significantly higher in patients who underwent oral anticoagulation therapy compared with patients without oral anticoagulation therapy (84% vs. 65%, P = 0.008 by log-rank test). Malignancy (odds ratio [OR], 2.789; P = 0.043) and immobilization (OR, 4.191; P = 0.029) were independent risk factors for delayed recanalization of CVT and oral anticoagulation (OR, 0.300; P = 0.020) was an independent factor in promoting recanalization in multivariate analysis. CONCLUSION For patients with isolated CVT, no oral anticoagulation resulted in higher rates of delayed recanalization compared to oral anticoagulation treatment. Immobilization and having malignancy were independent risk factors for delayed recanalization.