The place of helical CT scanning in acute pulmonary embolism

Pulmonary embolism is a relative common, potentially fatal disorder that clinicians have difficulty detecting and difficulty diagnosing. Deep venous thrombosis (DVT) is the most important source of thrombi. Early and accurate diagnosis is essential for efficient therapy. Therapy is based on long-term anticoagulation and has an important impact on the mortality and morbidity of pulmonary embolism. For the diagnosis of pulmonary embolism, the ventilation/perfusion (V/Q) scan is still the first examination in many instances. A normal V/Q scan or the combination of a low probability scan and a low clinical suspicion are associated with a prevalence of pulmonary embolism of 4%. The combination of a high-probability V/Q scan and a strong clinical suspicion has a prevalence of pulmonary embolism of 96%. All other results should be considered as non-diagnostic. However, the number of non-diagnostic V/Q examinations can be as high as 70%. Nevertheless, an additional pulmonary angiography will be performed in only in 15% of these cases. In the low pre-test probability group (poor clinical suspicion, absence of risk factors and no medical history) the V/Q scan is useful as a screening test ("rule-out" strategy). When the pre-test probability is higher or in other cases in which early diagnosis is necessary ("rule-in" strategy), a contrast-enhanced spiral CT of the pulmonary arteries (possibly in combination with ultrasonography of the lower limbs) is the most accurate examination.