Bibasilar Pleural Effusion: Etiology, Diagnosis, and Management

Bibasilar (bilateral basilar) pleural effusion is abnormal fluid accumulation in the dependent portions of both pleural spaces (costophrenic angles).

Pathophysiology

Fluid accumulates when pleural fluid formation exceeds lymphatic drainage capacity. Gravity causes preferential pooling at lung bases.

Common Causes (Transudate vs. Exudate – Light’s Criteria)

Transudate	Exudate
Congestive heart failure (most common)	Pneumonia (parapneumonic/empyema)
Cirrhosis (hepatic hydrothorax)	Malignancy (lung, breast, lymphoma, mesothelioma)
Nephrotic syndrome	TB pleuritis
Peritoneal dialysis	Pulmonary embolism (often unilateral)
Hypoalbuminemia	Autoimmune (SLE, RA), pancreatitis, post-CABG

Clinical Presentation

• Dyspnea (especially supine), orthopnea.
• Dullness to percussion, decreased breath sounds, egophony at bases.
• CXR: blunted costophrenic angles, meniscus sign; lateral decubitus confirms free fluid.
• Ultrasound: sensitive for small effusions; guides thoracentesis.

Management

1. Treat underlying cause (diuretics for CHF, antibiotics for parapneumonic).
2. Therapeutic thoracentesis if symptomatic (remove ≤1.5 L to avoid re-expansion pulmonary edema).
3. Chest tube for empyema / complicated parapneumonic.
4. Indwelling catheter (PleurX) for recurrent malignant effusions.
5. Pleurodesis (talc, doxycycline) for recurrent symptomatic effusions.

Diagnostic thoracentesis (cell count, protein, LDH, glucose, pH, cytology, cultures) guides etiology.