Case 27 Young woman with shortness of breath and chest pain

Effusions can be transudates (protein <30 g/L; e.g. in cardiac failure), exudates (>30 g/L; e.g. in infection, malignancy, pulmonary infarction), haemorrhagic (e.g. trauma, carcinoma) or chylous (e.g. due to obstructed thoracic duct caused by trauma, malignancy or parasites). Systemic diseases often cause bilateral effusions but can be unilateral.