[Incidence of pulmonary embolism in venous thrombosis]

The frequency of pulmonary embolism in patients with deep vein thrombosis can be assessed by pathological-anatomical and by nuclear medical studies. The frequency of deep vein thrombosis in autopsies ranges from 23.7% to 62%, by inclusion of microscopic thrombi the frequency increases to 72%. In most cases the localisation of the venous thrombosis is bilateral. In cases of venous thrombosis the frequency of pulmonary embolism is 52 to 79.4%, if microscopic thrombi are included, the number is 87.8%. 7.8% to 78.9% of all pulmonary emboli are considered as cause of death or severely contributing to death. The fatal embolisms originate preferentially from iliofemoral thrombosis. About 1/10 of all emboli originate from V. cava sup. and the right heart. In a small number of pulmonary emboli the origin could not be detected. The rate of correct intra vitam diagnosis is low, not more than 11 to 25% of all pathological-anatomical proven emboli had a correct diagnosis during life. In fatal pulmonary embolism the correct clinical diagnosis was made in 1/3. In nuclear medicine studies pulmonary embolisms are searched for from the clinical suspicion or the diagnosis of deep vein thrombosis with the perfusion-/ventilation- or inhalation scintigraphy. Patients with deep vein thromboses showed in 38 to 57.9% pulmonary embolism. In 80% of all pulmonary embolism multiple perfusion defects (2 to 9 perfusion defects) were detected, the lesions were evenly distributed in both lungs. The frequency of pulmonary embolism in calf vein thrombosis was 46%, in leg vein thrombosis 67% and reached 77% if the pelvic veins were involved. It is remarkable that the majority of all pulmonary emboli (46.3% to 100%) showed no clinical symptoms. The knowledge about the high frequency of pulmonary embolism in patients with deep vein thrombosis can improve the diagnosis of pulmonary embolism. For the diagnostic process of pulmonary embolism the presence of acute deep vein thrombosis increases the pre-test probability (prevalence of more than 50%). Every positive test for pulmonary embolism will gain a very high post-test probability according to Bayes' theorem.