Main characteristics of pleural fluid allowing to diagnose or exclude hepatic hydrothorax

Light’s criteria for exudative effusion if at least one criterion is present
Pleural fluid protein/serum protein ratio > 0.5
Pleural fluid LDH > 200 IU/L or > 2/3 serum LDH
Pleural fluid LDH/serum LDH > 0.6
Main characteristics of hepatic hydrothorax
Serum protein < 25 g/L
Pleural fluid protein/serum protein ratio < 0.5
Pleural fluid LDH < 200 IU/L
Pleural fluid LDH/serum LDH < 0.6
Albumin gradient (serum-pleural) > 11 g/L
Pleural fluid pH > 7.3
Neutrophils in pleural fluid < 500/mm3 with negative culture

LDH: lactate dehydrogenase. Hepatic hydrothorax is a transudative pleura effusion