Causes of Exudative Pleural Effusion
| Cause | Comment |
|---|---|
| Pleural infection (parapneumonic effusion and empyema) | Most common cause in young patients; empyema is defined as pus in the pleural cavity. |
| Malignancy | Most common cause in older patients and a frequent cause of massive effusions. |
| Tuberculosis | Delayed hypersensitivity reaction to mycobacteria released into the pleural space. AFB and pleural fluid culture often negative. |
| Chylothorax | Often milky effusions, diagnosis with presence of chylomicrons or pleural fluid triglyceride level >1.24 mmol/L. |
| Oesophangeal rupture | pH <7.20, increased levels of salivary amylase. |
| Pulmonary embolism | Almost always exudative; bloody in <50%; it should be suspected when dyspnoea is disproportionate to size of effusion, or when patient is hypoxic. |
| After coronary artery bypass surgery (CABG) | Commonly left sided pleural effusions and most resolve spontaneously.If <30 days of surgery, blood stained due to post-operative bleeding.If >30 days of surgery: clear fluid due to immune reaction. |
| Acute pancreatitis | Pleural fluid pancreatic amylase may be raised. |
| Rheumatoid arthritis | Typical low pleural fluid glucose (<1.6 mmol/L). |
| Yellow nail syndrome | Triad of nail discolouration, lymphoedema and pleural effusion. |