A patient is found to have a pleural effusion, a sample of the fluid is taken and sent to the laboratory for testing. The report states the patient has an exudate fluid [over 30g/L of protein], which is the most likely cause of this patients pleural effusion?

A) Left ventricular failure.
B) Metastatic breast cancer.
C) Superior vena cava obstruction.
D) Liver cirrhosis.
E) Hypothyroidism.


The answer is B. Pleural effusions can be split into transudates [under 30g/L of protein] and exudates [over 30g/L of protein], both have different causes.

Generally speaking the causes of transudate pleural effusions are systemic causes and can be remembered as failures:

• Cardiac failure [LVF or RVF]
• Renal failure
• Liver failure
• Hypothyroidism
• Hypoalbuminaemia.

Exudate pleural effusions are more likely to be local causes such as infection, neoplasia [primary or metastasis], autoimmune conditions, surgery or trauma.