What is Hydrothorax?
Hydrothorax, specifically hepatic hydrothorax, is the accumulation of transudative fluid (typically >500 mL) in the pleural space of patients with cirrhosis and portal hypertension, occurring in the absence of primary cardiac, pulmonary, or pleural disease. 1
Pathophysiology
The mechanism involves direct movement of ascitic fluid from the peritoneal cavity into the pleural space through small diaphragmatic defects, driven by the pressure gradient between positive intra-abdominal pressure and negative intrathoracic pressure during inspiration. 1, 2
Key anatomical features:
- Right-sided predominance occurs in approximately 73% of cases, with left-sided in 17% and bilateral in 10%. 2
- The diaphragmatic defects are typically small but allow continuous fluid passage from abdomen to chest. 1, 2
- The negative intrathoracic pressure during inspiration actively "pulls" ascitic fluid through these defects. 2
Clinical Characteristics and Fluid Analysis
Diagnostic fluid characteristics:
- The pleural fluid is a transudate with low protein content. 1
- Serum-to-pleural fluid albumin gradient is >1.1 g/dL, confirming transudative nature. 1, 3
- The pleural fluid may paradoxically have higher protein content than concurrent ascites due to hydrostatic pressure gradients. 2
Epidemiology and Prognosis
This condition affects approximately 5-12% of patients with advanced liver disease and carries a grave prognosis. 1, 4
Critical prognostic information:
- Median survival ranges from 8-12 months without liver transplantation. 1, 3, 4
- Standard prognostic scores like Child-Pugh and MELD significantly underestimate the poor outcomes associated with hepatic hydrothorax. 1
- 90-day mortality can reach 74% despite relatively modest MELD scores (median 14). 2
Clinical Presentation
Patients may be asymptomatic or present with respiratory symptoms including dyspnea, cough, hypoxemia, or frank respiratory failure when large effusions develop. 5
Important clinical pitfall: Unlike ascites where 5-8 liters can accumulate with minimal symptoms, only 1-2 liters of pleural fluid causes severe respiratory compromise. 6
Complications
Spontaneous bacterial empyema represents a serious complication requiring immediate recognition and antibiotic therapy, diagnosed using the same criteria as spontaneous bacterial peritonitis. 1, 3
Additional complications include progressive respiratory failure, pneumothorax from repeated thoracentesis, bleeding, and pleural/soft tissue infections. 1, 2