A 58-year-old man with a 10-year history of cirrhosis presents with progressive dyspnea. Chest X-ray shows a moderate right-sided pleural effusion. What is the most common cause of pleural effusion in this clinical scenario?

Explanation

## Most Common Cause of Pleural Effusion in Cirrhosis **Key Point:** Hepatic hydrothorax occurs in 5–12% of cirrhotic patients and is the most common cause of pleural effusion in this population, despite the absence of ascites in ~10% of cases. ### Pathophysiology The effusion develops via: 1. Transdiaphragmatic lymphatic channels that allow ascitic fluid to enter the pleural space 2. Increased portal pressure → ascites formation → fluid weeping through diaphragmatic defects 3. Right hemidiaphragm involvement in ~80% of cases (larger defects on right) ### Key Features | Feature | Hepatic Hydrothorax | | --- | --- | | **Laterality** | Right > Left (80% right-sided) | | **Ascites present** | May be absent in 10% | | **Fluid characteristics** | Transudative (low protein, LDH) | | **Mechanism** | Diaphragmatic defects + portal hypertension | | **Management** | Salt restriction, diuretics, TIPS if refractory | **Clinical Pearl:** The absence of ascites does NOT rule out hepatic hydrothorax — some patients have isolated pleural effusion due to preferential flow through diaphragmatic defects. **High-Yield:** Hepatic hydrothorax is a **transudative effusion** (protein <2.5 g/dL, LDH <200 IU/L) — this distinguishes it from empyema (exudative, infected) or malignancy (exudative, cytology positive). ### Differential Diagnosis in Cirrhosis - **Spontaneous bacterial empyema:** Occurs in ~5% of cirrhotic pleural effusions; requires positive culture or PMN >250/μL - **Pulmonary embolism:** Less common; would show wedge-shaped opacity + effusion - **Malignancy:** Separate diagnosis; would require cytology confirmation