Outcome after bilateral deep vein thrombosis

Background: The aim of our study was to assess how often deep vein thrombosis (DVT) occurs bilaterally and if this has an impact on the recurrence rate of thromboembolic disease and on the occurrence of malignant tumors. Additionally, the occurrence of pulmonary embolism and mortality of patients was assessed. Patients and methods: For this observational study, we retrospectively screened all patient's records for DVT, investigated between 2000 and 2017. 2409 patients with the diagnosis of DVT were found. The patients aged between 18 and 89 years old in 2017, received a follow-up questionnaire, asking for thromboembolic recurrence, malignant tumors and pulmonary embolism. 755 patients were included in the follow-up cohort (604 with unilateral, 151 with bilateral DVT). We performed nonparametric tests to assess two group analysis. Results: Bilateral DVT occurred in 19% of the patients in this cohort. Patients with bilateral DVT develop significantly more often cancer, either at the time of diagnosis or in the follow up, compared to patients with unilateral DVT (22.5% vs. 15.4%, p=0.036). They also endure significantly more often pulmonary embolism simultaneously (33.8% vs. 20.8%, p<0.001). Patients with bilateral DVT were significantly older (median 69 years) than patients with unilateral DVT (median 63 years, p<0.001). In addition, patients with bilateral DVT show a higher mortality (9.1% vs. 5.2%, p=0.002), a higher recurrence rate could not be observed. Conclusions: Bilateral DVT is more common than published so far. Patients with bilateral DVT suffer more often from malignant tumors, and are more often diagnosed with pulmonary embolism. The patients with bilateral DVT are older and have a higher mortality. Further investigations should address the issue of recurrent thromboembolic disease in a prospective cohort study.