Approach to Pleural Effusion
Begin with clinical assessment to determine if the effusion is likely transudative (bilateral effusions with heart failure, cirrhosis, or renal failure do not require thoracentesis unless atypical features present), then proceed to ultrasound-guided thoracentesis for all unilateral effusions or bilateral effusions with normal heart size to differentiate transudate from exudate using Light's criteria. 1, 2
Initial Clinical Assessment
Key historical and examination features to identify:
- Drug history: Multiple medications cause exudative effusions (amiodarone, nitrofurantoin, methotrexate, among others) 1
- Pleuritic pain with dyspnea disproportionate to effusion size: Suggests pulmonary embolism (75% have pleuritic pain, effusions typically occupy <1/3 hemithorax) 1
- Bilateral effusions with clinical heart failure: If strongly suggestive of transudate, aspiration not needed unless atypical features or failure to respond to therapy 1
Imaging Strategy
Chest radiography first, followed by point-of-care ultrasound:
- Chest X-ray determines laterality and detects moderate-to-large effusions 2
- Ultrasound is mandatory for all pleural interventions and detects small effusions, features suggesting complicated effusion or malignancy 3, 2
- CT chest when needed to exclude other causes of dyspnea or suggest complicated parapneumonic/malignant effusion 2
Diagnostic Thoracentesis
Perform ultrasound-guided thoracentesis for:
- Any unilateral effusion 1, 3
- Bilateral effusions with normal heart size 3
- Transudative-appearing effusions with atypical features or treatment failure 1
Routine pleural fluid analysis must include:
- Gross appearance and odor 3
- Cell count with differential 3, 2
- Total protein, LDH, glucose, pH 3, 2
- Gram stain and culture 2
- Cytology (obtain 25-50 mL for optimal yield) 3
Apply Light's criteria to differentiate exudate from transudate 2
Therapeutic Considerations During Initial Thoracentesis
- Limit removal to 1.5L maximum to prevent re-expansion pulmonary edema 3
- Remove fluid at approximately 500 mL/hour if using continuous drainage 3
Algorithm for Undiagnosed Exudative Effusions
If initial thoracentesis non-diagnostic:
Second thoracentesis increases cytology yield (consider before invasive procedures) 1, 3
Image-guided pleural biopsy if CT shows pleural thickening or nodules/masses 1
Thoracoscopy (medical or surgical) when less invasive tests fail:
Closed pleural biopsy (Abrams) alternative:
Bronchoscopy: Limited Role
Do NOT perform routine bronchoscopy for undiagnosed pleural effusion 1
Bronchoscopy indicated only when:
- Hemoptysis present 1
- Radiographic evidence of bronchial obstruction, mass, or volume loss 1
- Large effusion without contralateral mediastinal shift (suggests endobronchial obstruction) 1
Yield is <5% in isolated pleural effusion without pulmonary abnormality or hemoptysis, compared to 61% yield from pleural investigation 1
Special Considerations for Parapneumonic Effusions
pH <7.2 indicates complicated parapneumonic effusion requiring:
- Prompt consultation for catheter or chest tube drainage 2
- Possible tissue plasminogen activator/deoxyribonuclease therapy 2
- Thoracoscopy if drainage inadequate 2
Hemorrhagic Effusions
Leading malignant causes in order: lung cancer, breast carcinoma, mesothelioma 3
- Mesothelioma has particular propensity for hemorrhagic effusions 3
- Critical pitfall: 40% of needle incisions for mesothelioma investigation become invaded by tumor—minimize number of interventions 1
Management of Recurrent Malignant Effusions
For symptomatic recurrence with expandable lung: