Can pulmonary embolism be seen on a chest X‑ray?

Can Pulmonary Embolism Be Seen on Chest X-ray?

Chest X-ray is rarely diagnostic for pulmonary embolism and should never be used alone to diagnose or exclude PE; its primary value is to identify alternative diagnoses such as pneumonia, pneumothorax, or heart failure. 1, 2

Diagnostic Limitations of Chest X-ray

• The chest radiograph is abnormal in 88% of PE cases, but the findings are non-specific and overlap significantly with other cardiopulmonary conditions. 2

• No single chest X-ray finding reliably confirms or excludes PE—atelectasis/infiltrate occurs in 49% of PE patients but also in 45% of non-PE patients, making it essentially useless for discrimination. 2

• The most commonly cited "classic" signs have poor sensitivity and specificity:

  • Hampton's hump (pleural-based wedge-shaped opacity from pulmonary infarction) appears in only 23% of PE cases 1
  • Westermark sign (decreased pulmonary vascularity) is present in 36% of PE cases 1
  • Fleischner sign (amputation of hilar artery) occurs in 36% of PE cases but only 1% of non-PE cases, making it more specific but still insensitive 1

• Pleural effusion (46% of PE cases) and elevated diaphragm (36%) are common but equally non-specific. 1

Clinical Utility of Chest X-ray in the PE Workup

The main role of chest radiography is to exclude alternative diagnoses that mimic PE clinically, including pneumonia, pneumothorax, lobar collapse, heart failure, rib fracture, and aortic dissection. 1, 2

• Chest X-ray is essential for interpreting ventilation-perfusion (V/Q) scans, as abnormalities on the radiograph affect V/Q scan interpretation and classification. 3, 1

• A normal chest X-ray in an acutely dyspneic, hypoxic patient with risk factors paradoxically increases the pre-test probability of PE and should heighten clinical suspicion rather than provide reassurance. 3, 1

Definitive Imaging Requirements

• CT pulmonary angiography (CTPA) is now the recommended first-line imaging modality for suspected PE, regardless of chest X-ray findings. 3, 1

• Patients with a good-quality negative CTPA do not require further investigation or anticoagulation for PE. 1

• V/Q scanning remains a valid alternative when CTPA is contraindicated (e.g., contrast allergy, renal insufficiency) or unavailable. 3

Clinical Algorithm

1. Assess clinical probability using validated tools (Wells score or revised Geneva score) and document the pre-test probability. 1

2. Obtain chest X-ray to evaluate for alternative diagnoses (pneumonia, pneumothorax, heart failure), not to diagnose PE. 1, 2

3. For low/intermediate probability patients: obtain D-dimer; if negative, PE is excluded and no imaging is needed. 1

4. For high probability patients or positive D-dimer: proceed directly to CTPA within 24 hours (or within 1 hour if massive PE with hemodynamic instability). 1

5. Never delay anticoagulation based on chest X-ray findings alone—definitive imaging with CTPA is mandatory before withholding therapy. 1

Common Pitfalls to Avoid

• Do not rely on a normal chest X-ray to exclude PE—only 12% of PE patients have a completely normal radiograph. 2

• Do not use chest X-ray findings to guide anticoagulation decisions—this requires definitive imaging with CTPA or V/Q scan. 1

• Do not assume that classic signs (Hampton's hump, Westermark sign) must be present—their absence does not reduce the likelihood of PE in a patient with appropriate clinical features. 1, 2

• In young patients (<40 years) with isolated pleuritic pain, no risk factors, respiratory rate <20/min, and a normal chest X-ray, PE is very unlikely and empiric anticoagulation can be safely avoided. 3