Pulmonary thromboembolism—more commonly known as pulmonary embolism (PE) — and deep-venous thrombosis (DVT) are different clinical manifestations of a single disease entity, venous thromboembolic disease. Pulmonary embolism is considered the "third most common acute cardiovascular disease after ischemic heart disease and stroke" [1]. Unlike ischemic heart disease and stroke, however, venous thromboembolic disease has traditionally been diagnosed with imaging techniques that have limited sensitivity and specificity. Because it has been difficult to make a diagnosis of venous thromboembolic disease, understanding of its epidemiology and natural history has been limited. The development of helical computed tomographic pulmonary angiogra-phy (CTPA) for PE has rapidly changed the workup of patients with suspected thromboembolic disease, while posing new treatment dilemmas.
The pathogenesis of venous thromboembolic disease begins with the development of DVT. DVT usually arises in the deep-venous system of the lower extremities. Risk factors for the development of DVT include malignancy and other hypercoagulable states, immobility, and venous injury.
DVT becomes a potentially life-threatening entity when clots detach from their points of origin and embolize to the lungs. Diagnosis of thromboembolic disease, therefore, has two arms: the diagnosis of PE and the diagnosis of DVT. Both are important, but it can be argued that, in patients who have survived an initial embolic event, the diagnosis of DVT is more important than the diagnosis of PE, as the next em-bolus may have devastating consequences.
Diagnosis of the two entities historically has been approached separately. The recent innovation, however, of delayed venous imaging (CT venography [CTV]) after CTPA has resulted in the development of a single diagnostic tool that can be used for a complete evaluation of thromboembolic disease.
This article briefly reviews the range of diagnostic tests other than CT that are used in evaluating patients with suspected thromboembolic disease. The sensitivity and specificity of CTPA is compared with other techniques. In addition, CTV is discussed. The authors review the design of protocols for performing CTPA and CTV. Findings of acute and chronic thromboembolic disease are discussed as well as pitfalls in interpretation.