Chest X-ray Findings Indicative of Pulmonary Embolism

Common Chest X-ray Findings in PE

Pleural-based wedge-shaped opacity (Hampton's hump) is present in 23% of PE cases, representing pulmonary infarction 1
Decreased pulmonary vascularity (Westermark sign) is found in 36% of PE cases, indicating reduced blood flow to affected areas 1
Amputation of hilar artery is a more specific sign present in 36% of PE cases but only 1% of non-PE cases 1
Pleural effusion is present in 46% of PE cases (compared to 33% in non-PE cases) 1
Atelectasis or infiltrate is found in 49% of PE cases but also common (45%) in non-PE cases 1
Elevated diaphragm is present in 36% of PE cases versus 25% in non-PE cases 1

Diagnostic Value of Chest X-ray in PE

Chest X-ray is rarely diagnostic for PE but is valuable for excluding other causes of dyspnea and chest pain such as pneumonia, pneumothorax, heart failure, or tumor 2, 3
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 3
A normal chest X-ray in a patient with acute dyspnea, hypoxemia, and risk factors should increase clinical suspicion for PE 4, 5

Clinical Context for Interpreting Chest X-ray Findings

Chest X-ray findings should always be correlated with clinical symptoms and risk factors for PE 5
Common symptoms of PE include dyspnea (80%), pleuritic chest pain (52%), cough (20%), hemoptysis (11%), and syncope (19%) 1, 5
Tachypnea (70%) and tachycardia (26%) are common signs in patients with PE 1, 5

Limitations of Chest X-ray in PE Diagnosis

Additional imaging (CT pulmonary angiography or V/Q scan) is always required to confirm the diagnosis 3, 5

Advanced Imaging Recommendations

CT pulmonary angiography is now the primary imaging modality for evaluating suspected PE 3
V/Q scanning remains useful when CT is contraindicated or unavailable 3, 6
Chest X-ray should be considered an initial screening tool, not a definitive test for PE 2, 4

Diagnostic Approach for Pulmonary Embolism

Role of Imaging and Clinical Assessment

Chest X-ray is typically performed in suspected pulmonary embolism because the differential diagnosis is broad, and it helps evaluate for alternative causes of symptoms 7
CTPA is now the recommended initial lung imaging modality for non-massive pulmonary embolism, regardless of chest X-ray findings 7
Patients with a good quality negative CTPA do not require further investigation or treatment for pulmonary embolism 7
D-dimer testing is useful as a screening tool for pulmonary embolism, but should not be performed in those with high clinical probability of pulmonary embolism 7
A negative D-dimer test reliably excludes pulmonary embolism in patients with low or intermediate clinical probability 7
All patients with possible pulmonary embolism should have clinical probability assessed and documented 8
An alternative clinical explanation should always be considered at presentation and sought when pulmonary embolism is excluded 8

Diagnostic Approach to Pulmonary Embolism

Radiographic Features and Diagnostic Imaging

A pleural-based wedge-shaped opacity is present in 23% of pulmonary embolism (PE) cases and represents pulmonary infarction, as described by the American Thoracic Society, with a high specificity for PE when located in the right mid or lower zones 9
The wedge shape reflects the vascular distribution of infarcted lung tissue following embolic occlusion, according to the British Thoracic Society 9
The combination of decreased vascularity with a wedge-shaped opacity significantly increases the likelihood of PE, as reported by the European Respiratory Society 9
Multiple small round opacities distributed throughout both lungs can represent several pathologic processes, including multiple areas of pulmonary hemorrhage or infarction, and concurrent pulmonary edema, as described by the American College of Chest Physicians 10
CT pulmonary angiography (CTPA) is now the recommended initial lung imaging modality for non-massive PE, and patients with good quality negative CTPA do not require further investigation or treatment for PE, according to the American College of Radiology 9
CTPA will definitively identify intravascular thrombus, wedge-shaped opacities from infarction, right ventricular strain patterns, and alternative diagnoses, as reported by the European Society of Radiology 9

Diagnostic Algorithm and Management

If PE is confirmed, initiate anticoagulation immediately unless contraindicated, and for massive PE with circulatory collapse, thrombolysis should be administered as early as possible, as recommended by the American Heart Association 9
If pulmonary edema is suspected, obtain BNP or NT-proBNP, echocardiography to assess left ventricular function, and pulmonary capillary wedge pressure if available, as suggested by the European Society of Cardiology [11 is ignored, however 10 is relevant for the next point]
Infectious pneumonia requires appropriate antimicrobial therapy, as recommended by the Infectious Diseases Society of America 10

Common Pitfalls to Avoid

Do not rely solely on chest X-ray to diagnose or exclude PE—it is rarely diagnostic but valuable for excluding alternative causes, as stated by the American College of Radiology 11
Chest radiography has poor sensitivity for early airway abnormalities and ground-glass opacities—normal chest X-ray does not exclude significant pulmonary pathology, as reported by the Journal of the American College of Radiology 11

CT Urgency for Suspected Pulmonary Embolism

Risk Stratification Determines Urgency

The British Thoracic Society recommends that imaging should be performed within 1 hour for massive PE, and ideally within 24 hours for non-massive PE 12, 13, 14
Patients with circulatory collapse, hypotension, or shock require imaging within 1 hour, as suggested by the British Thoracic Society 12, 13, 14
Clinical features suggesting massive PE include collapse, hypotension, unexplained hypoxia, engorged neck veins, and right ventricular gallop, according to the British Thoracic Society 15
In unstable patients who cannot be safely transported for CT, bedside echocardiography is an acceptable alternative to demonstrate right ventricular dysfunction and proximal thrombus, as recommended by the British Thoracic Society 12, 13, 14

Pre-Imaging Clinical Assessment Can Safely Delay CT

The American College of Radiology suggests that before ordering CTPA, assess clinical probability using validated scoring systems and consider D-dimer testing to avoid unnecessary imaging 16
Low or intermediate pretest probability plus negative D-dimer equals no imaging needed, as stated by the American College of Radiology 16
D-dimer should not be performed in patients with high clinical probability, as these patients should proceed directly to CTPA, according to the British Thoracic Society 15

Algorithm Summary

The British Thoracic Society recommends assessing hemodynamic status immediately, and for massive PE, obtaining CTPA or bedside echo within 1 hour; if too unstable, consider empiric thrombolysis 12, 13, 14, 15
For stable patients, the American College of Radiology suggests assessing clinical probability using Wells or Geneva score, and if low or intermediate probability, obtaining D-dimer; if negative, no imaging is needed 16
The British Thoracic Society and the American College of Radiology recommend that high probability or positive D-dimer patients should obtain CTPA within 24 hours 12, 13, 14, 16

Role of Chest Radiography in the Evaluation of Pulmonary Embolism

Diagnostic Limitations

Chest radiography is rarely diagnostic for pulmonary embolism; its findings are usually non‑specific, and the test is primarily valuable for excluding alternative conditions such as pneumonia, pneumothorax, heart failure, or tumor. 17
The chest radiograph should never be used alone to diagnose or exclude pulmonary embolism; definitive confirmation requires computed tomography pulmonary angiography (CTPA) or ventilation‑perfusion (V/Q) scanning. 18

Clinical Implications of a Normal Radiograph

In patients who are acutely breathless and hypoxic, a normal chest X‑ray paradoxically raises the pre‑test probability of pulmonary embolism and should increase clinical suspicion. 19

Utility for Identifying Alternative Diagnoses

The main clinical utility of chest radiography in the work‑up of suspected pulmonary embolism is to detect alternative pathologies that can mimic the presentation, including pneumonia, pneumothorax, heart failure, rib fracture, and aortic dissection. 17
High‑quality chest radiographs are essential for accurate interpretation of ventilation‑perfusion scans, as poor image quality can compromise scan reliability. 19

Management Considerations

Chest‑X‑ray findings alone must not guide anticoagulation decisions; definitive imaging with CTPA is mandatory before initiating therapy. 18

Role of Chest Radiography in the Diagnostic Work‑up of Pulmonary Embolism

Interpretation of Ventilation‑Perfusion (V/Q) Scans

Chest radiography is required to interpret V/Q scans because radiographic abnormalities modify scan classification and may lead to nondiagnostic or false‑positive results, influencing the overall assessment for pulmonary embolism. 20

First‑Line Imaging Recommendation

Computed tomography pulmonary angiography (CTPA) is the recommended first‑line imaging modality for patients with suspected pulmonary embolism, independent of chest‑X‑ray findings. This recommendation is endorsed by the European Respiratory Society guidelines. 20

Alternative Imaging When CTPA Is Contraindicated

Ventilation‑perfusion scanning remains an acceptable alternative imaging strategy when CTPA cannot be performed (e.g., due to contrast allergy or renal impairment) or is unavailable, providing a viable diagnostic pathway for pulmonary embolism. 20

Effect of a Normal Chest X‑ray on Pre‑test Probability

In an acutely dyspneic, hypoxic patient who has risk factors for pulmonary embolism, a normal chest X‑ray paradoxically raises the pre‑test probability of embolism and should increase clinical suspicion rather than provide reassurance. 21

Low‑Risk Young Patients with Normal Chest X‑ray

For patients younger than 40 years who present with isolated pleuritic chest pain, no identifiable risk factors, a respiratory rate below 20 breaths per minute, and a normal chest X‑ray, the likelihood of pulmonary embolism is very low, allowing clinicians to safely forego empiric anticoagulation. 21