ACR Codes: 68.721
The diagnostic approach and treatment for pulmonary embolism continues to be an evolving and controversial area in medicine. Current recommendations are based on numerous studies, such as the PIOPED study. Imaging modalities vary and can be situation or institution dependent. The initial work-up for a pt suspected of having a pulmonary embolism involves a CXR in order to rule out other pulmonary or cardiac findings, such as a pneumothorax, pneumonia, or rib fracture. If the CXR is non diagnostic, other imaging modalities include V/Q scan, helical CT with PE protocol, pulmonary angiography, echocardiography, or venous US of the lower extremities. The gold standard is generally thought to be pulmonary angiography. There are advantages and disadvantages to each modality. CXR is rarely diagnostic of PE, nor does it often show the classic findings (Hampton’s hump, Westermark’s sign). However, it can be useful for ruling out other pathology. The most common findings on CXR in pt’s with PE include atelectasis, pleural effusions, infiltrates, and elevation of the hemidaphragm. V/Q scans also are rarely diagnostic. The scans can be difficult to interpret and often meaningless if there is other underlying pulmonary pathology. Additionally, the diagnosis of PE was highly dependent on the clinical suspicion of the physician. More recently, helical CT has been used to aid in diagnosing PE. Disadvantages include poor visualization of the periphery of the lungs at the subsegmental level. The main advantage is the relative ease of the procedure and the decreased variable of reader interpretation (when compared to V/Q scans). As previously stated, pulmonary angiography continues to be the gold standard for diagnosing pulmonary emboli. However, these studies are slightly more invasive than other modalities and can carry up to a 0.5% risk of mortality.
Reference(s): Pulmonary Thromboembolism, Samuel Z. Goldhaber, Harrison’s Principles of Internal Medicine, 14th edition, 1998, 1469-72. Plantz, Scott H., Emergency Medicine, Williams & Wilkins, 1998, 118-122.
UpToDate, ATS Guidelines: The diagnostic approach to acute venous thrombembolism
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