Collagen vascular disease
Suppurative pleuritis (empyema)
Hemorrhagic pleuritis : Tumor
Hydrothorax : Transudate, eg Congestive heart failure
Hemothorax ,eg, aortic aneurysm, trauma
Chylothorax : Tumor obstructing normal lymphatics
Transudative effusion vs exudative effusion, and Light’s criteria( protein less than 50% of plasma, and LDH less than two third of plasma is labelled a transudate, else it is called an exudate).