When would you consider pulmonary embolism (PE) in a patient with worsening pleural effusion?

When to Consider Pulmonary Embolism in a Patient with Worsening Pleural Effusion

Pulmonary embolism (PE) should be strongly considered in any patient with worsening pleural effusion, especially when accompanied by pleuritic chest pain, unexplained dyspnea, or hypoxia, as PE is the most commonly overlooked disorder in patients with pleural effusion. 1

Clinical Presentation Suggesting PE in Patients with Pleural Effusion

• The presence of pleuritic chest pain in a patient with a pleural effusion is highly suggestive of pulmonary embolism 1
• Worsening dyspnea (present in approximately 72% of PE cases) that is unexplained by other causes should prompt consideration of PE 2
• Nearly all pleural effusions due to PE are exudates, frequently hemorrhagic, and often show marked mesothelial hyperplasia 1
• Patients with pleural effusion due to PE are likely to have emboli in central, lobar, segmental, or subsegmental pulmonary arteries 1

Risk Factors That Should Increase Suspicion

• Recent immobilization for more than one week 3
• History of previous venous thromboembolism 3
• Recent surgery or lower limb trauma/surgery 3
• Pregnancy or postpartum period 3
• Major medical illness 3
• Hormone therapy (especially in young women) 3, 4
• Unexplained worsening of pre-existing heart failure or pulmonary disease 4

Warning Signs That Should Prompt Immediate Investigation

• Hemodynamic instability (hypotension, shock) with a pleural effusion of unclear etiology 3
• Syncope (even transient) in a patient with pleural effusion 4
• Unexplained hypoxemia with a normal chest radiograph (aside from the effusion) 3
• Tachypnea (respiratory rate >20/min) with pleural effusion 3

Diagnostic Approach When PE is Suspected

1. Assess clinical probability using a validated tool (Wells score or Geneva score) 3, 5

2. For patients with low/intermediate clinical probability:

   • Perform D-dimer testing - a negative result using a validated test can exclude PE 3
   • Note that D-dimer may be elevated for various reasons other than PE 6

3. For patients with high clinical probability or positive D-dimer:

   • Computed Tomography Pulmonary Angiography (CTPA) is the gold standard imaging modality 6
   • Ventilation-perfusion (V/Q) scan can be used when CTPA is contraindicated 6
   • Consider leg ultrasound if clinical signs of DVT are present 3

Important Clinical Pitfalls to Avoid

• Do not dismiss the possibility of PE just because symptoms are mild or transient - PE can present with symptoms that fluctuate or resolve temporarily 4
• Do not rule out PE based solely on absence of risk factors - approximately 40% of patients with PE have no predisposing factors 2
• The presence of bloody pleural fluid is not a contraindication for anticoagulation therapy if PE is diagnosed 1
• Do not assume that an alternative diagnosis (such as pneumonia) excludes PE - they can coexist 7
• Remember that in patients with pre-existing heart failure or lung disease, worsening dyspnea may be the only symptom indicating PE 2

Management Considerations

• Anticoagulation should be started promptly when PE is strongly suspected, even while diagnostic workup is ongoing, unless there are contraindications 3
• Direct oral anticoagulants (DOACs) are preferred over traditional heparin-vitamin K antagonist regimens for most patients 3
• No specific treatment is required for the pleural effusion itself beyond treating the underlying PE 1
• Thrombolysis should be considered in patients with PE and hemodynamic instability 3

By maintaining a high index of suspicion for PE in patients with worsening pleural effusion, particularly when accompanied by risk factors or concerning symptoms, clinicians can avoid missing this potentially fatal but treatable condition.