The initial CXR is normal in nearly one-third of patients with PE. 7 A normal CXR in the setting of dyspnea and hypoxemia without evidence of reactive airway disease is strongly suggestive of PE.12 The overwhelming majority of patients will develop some CXR abnormality during the course of their disease. 13 Infiltrate or atelectasis will appear in nearly 50 percent, while an elevated hemi-diaphragm occurs in about 40 percent, often in association with a pleural effusion. 7
The classically described Hampton hump, a pleural-based wedge-shaped infiltrate, is uncommon. The Westermark sign, relative oligemia distal to engorged pulmonary arteries, may be seen in patients with massive PE (Fig..52:l). The CXR is of greatest utility in ruling in other causes of the patient's complaints, such as pneumothorax or pneumonia. It is essential for the subsequent interpretation of lung scans and pulmonary arteriograms.
FIG. 52-1. Westermark sign: AP CXR demonstrating relative oligemia in right upper lobe and dilated proximal pulmonary artery.
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