What are the next steps for a patient with bilateral pleural effusions?

Management of Bilateral Pleural Effusions

For a patient with bilateral pleural effusions on ultrasound, the first step is to determine whether the effusion is likely a transudate or exudate through clinical assessment, and if the clinical picture does not strongly suggest a transudate, proceed with diagnostic thoracentesis to guide further management. 1, 2

Initial Evaluation

Clinical Assessment

• Evaluate for clinical features suggesting transudative effusions:
  • Heart failure (most common cause of bilateral effusions)
  • Hypoalbuminemia
  • Renal failure requiring dialysis
  • Liver cirrhosis

Important Considerations

• Do not perform thoracentesis if the clinical picture strongly suggests a transudate (e.g., clear heart failure) unless there are atypical features or failure to respond to therapy 1
• Take a detailed drug history as medications can cause exudative pleural effusions 1, 2
• Consider pulmonary embolism if patient has pleuritic pain and dyspnea out of proportion to effusion size 1

Diagnostic Algorithm

Step 1: Clinical Assessment and Imaging

• Review ultrasound findings for:
  • Size of effusions
  • Presence of loculations or septations
  • Pleural thickening or masses

Step 2: Determine Need for Thoracentesis

• If clinical picture strongly suggests transudate → Treat underlying cause
• If clinical picture unclear or suggests exudate → Proceed with thoracentesis

Step 3: Diagnostic Thoracentesis

• Perform ultrasound-guided thoracentesis using a fine bore (21G) needle and 50ml syringe 1, 2
• Send samples in both sterile vials and blood culture bottles for:
  • Protein and LDH (to differentiate transudate from exudate)
  • pH (especially if infection suspected)
  • Glucose
  • Cell count with differential
  • Gram stain and culture
  • Cytology for malignant cells
  • AAFB stain and TB culture if tuberculosis suspected 1

Interpretation and Management

If Transudate (meets Light's criteria):

• Most commonly due to heart failure, cirrhosis, or hypoalbuminemia
• Treat the underlying cause (e.g., diuretics like furosemide for heart failure) 3
• Monitor response to treatment

If Exudate:

• Further investigation based on pleural fluid analysis:
  • Malignancy: Consider CT scan of thorax (with contrast) with fluid present for better visualization of pleura 1, 2
  • Infection: If pH < 7.2 or purulent fluid, consider chest tube drainage 2
  • Tuberculosis: Send for AAFB stain and TB culture
  • Chylothorax: Check triglyceride levels if milky fluid

If Diagnosis Remains Unclear:

• Refer to chest physician 1
• Consider contrast-enhanced CT thorax
• Consider pleural biopsy (ultrasound/CT guided, closed pleural biopsy, or thoracoscopy)

Common Pitfalls to Avoid

• Performing thoracentesis on bilateral effusions when clinical picture strongly suggests transudate (e.g., clear heart failure) 1, 2
• Failing to consider pulmonary embolism as a cause of exudative effusion 1
• Not recognizing that bilateral effusions often have multiple etiologies (83% have two or more causes) 4
• Overlooking malignancy as a common cause of exudative bilateral effusions 4
• Delaying drainage in complicated parapneumonic effusions or empyema 2

Special Considerations During COVID-19

• In patients with suspected or confirmed COVID-19, pleural effusion is uncommon (5.3-5.8% of cases) 1
• When performing pleural procedures in COVID-19 patients:
  • Use full personal protective equipment
  • Perform procedures in a negative pressure room if available
  • Use trained staff to minimize procedure duration and complications 1

Remember that the prognosis for patients with exudative pleural effusions depends on the underlying cause, with malignant effusions carrying a poorer prognosis (median survival 3-12 months) 2.