Thank you to Dr. Pat Liu for presenting a complex case where hepatic hydrothorax resulted in acute hypoxemic respiratory failure and hepatic encephalopathy.
Pleural effusions occur in the setting of cirrhosis in 5-10% of cases. They typically occur on the right side (73-85%) but can be on the left (13-17%) or rarely bilateral (2-10%). Beyond clinical context, the pleural fluid analysis is quite helpful. Hepatic hydrothorax is typically transudative with the following characteristics:
However, every good Internist knows not to miss an exudative effusion. So, don't forget to check Light's Criteria:
- pleural fluid to protein ration greater than 0.5
- pleural fluid to LDH ratio greater than 0.6
- LDH greater than 2/3 the upper limit of normal
In this case, the fluid was exudative by LDH value. According to a study by Bielsa in Respirology (2012), 20-30% of transudates from hepatic hydrothorax or heart failure are mischaracterized as exudates. In this case they suggest measuring the Albumin and calculating the pleural fluid to Albumin ratio.
This way, you don't forget to think about exudates (Light's Criteria is generally quite sensitive but less specific) however, you accurately classify the pleural fluid. And, generally these "false exudates" are seen in individuals who are receiving diuretic therapy (as in our patient) or have bloody effusions.