What are the typical chest x-ray findings in pulmonary embolism?

Chest X-ray Findings in Pulmonary Embolism

Chest X-ray is rarely diagnostic for pulmonary embolism but is valuable for excluding other causes of dyspnea and chest pain such as pneumonia, pneumothorax, heart failure, or tumor. 1

Common Radiographic Findings

• A normal chest radiograph is present in only 12% of patients with pulmonary embolism (PE), but a normal chest X-ray in an acutely breathless hypoxic patient should increase clinical suspicion for PE 1, 2

• Pleural-based wedge-shaped opacity (Hampton's hump) is present in approximately 23% of PE cases, representing pulmonary infarction 1, 3

• Decreased pulmonary vascularity (Westermark sign) is found in 36% of PE cases, indicating reduced blood flow to affected areas 1, 4

• Amputation of hilar artery (Fleischner sign) is a more specific sign present in 36% of PE cases but only 1% of non-PE cases 1, 2

• Pleural effusion is present in 46% of PE cases (compared to 33% in non-PE cases) 1, 4

• Atelectasis or infiltrate is found in 49% of PE cases but is also common (45%) in non-PE cases 1, 4

• Elevated diaphragm is present in 36% of PE cases versus 25% in non-PE cases 1, 5

• Cardiomegaly may be present but is nonspecific 6

Diagnostic Value and Limitations

• The main utility of chest X-ray is to aid in the interpretation of ventilation-perfusion scans, as abnormalities on chest X-ray can affect V/Q scan interpretation 1, 2

• Chest X-ray findings are usually non-specific in PE and may be normal, especially in early or small emboli 5, 1

• Common findings like atelectasis, infiltrates, and pleural effusions have poor specificity for PE as they occur at similar rates in patients without PE 2

• The chest radiograph is essential for two purposes: identifying alternative diagnoses and providing context for interpreting V/Q scans 6, 2

Clinical Context for Interpretation

• Chest X-ray findings should always be correlated with clinical symptoms and risk factors for PE 1

• Common symptoms of PE include dyspnea (80%), pleuritic chest pain (52%), cough (20%), hemoptysis (11%), and syncope (19%) 4

• Tachypnea (70%) and tachycardia (26%) are common signs in patients with PE 4

• A normal chest radiograph in a patient with unexplained dyspnea, hypoxemia, and risk factors should raise suspicion for PE 5, 1

Diagnostic Algorithm

1. Obtain chest X-ray in all patients with suspected PE 5

2. If chest X-ray is normal in a patient with unexplained dyspnea and hypoxemia, increase suspicion for PE 5, 1

3. If chest X-ray shows specific signs (Hampton's hump, Westermark sign, or Fleischner sign), consider PE more likely 1, 2

4. Regardless of chest X-ray findings, proceed with additional diagnostic testing (D-dimer testing in appropriate patients and/or imaging) 4

5. Use chest X-ray findings to aid in interpretation of V/Q scans if this modality is selected 2

Important Caveats

• Never exclude PE based solely on chest X-ray findings, even if the radiograph is normal 1, 2

• CT pulmonary angiography (CTPA) remains the first-line diagnostic imaging tool for suspected PE regardless of chest X-ray findings 4

• V/Q scanning may be preferred when CT is contraindicated (pregnancy, severe renal failure, contrast allergy) 5, 1

• Chest X-ray findings in PE may be difficult to interpret in patients with pre-existing cardiopulmonary disease 5

• The interpretation of chest X-ray findings should always be integrated with clinical probability assessment and other diagnostic tests 5, 1