Pleural Effusion and Pleural Disease
Pleural effusion is where there's a collection of fluid in the pleural cavity. It can be classed into 2 types:
Transudative - more likely to be bilateral, with less protein (< 35g/L) and LDH
Exudative - more likely to be unilateral, with a lot more protein (> 35g/L) and LDH
N.B. If the protein content is equivocal (25-35 g/L), the Light's criteria can be applied to work out if it's an exudative effusion or not.
Pleurisy is the inflammation of the pleura, which impairs its lubricating function, leading to a sharp pleuritic chest pain.
Types
Transudative effusion - Imbalance of the pressure changes that govern fluid shifts, which results in fluid moving across into the pleural space. This can be due to:
Increased capillary hydrostatic pressure (water forced out of vessels) e.g. Congestive HF
Increased capillary oncotic pressure (water isn’t reabsorbed into vessels) e.g. Cirrhosis, Nephrotic Syndrome, CKD, GI malabsorption/malnutrition (These all cause Hypoalbuminaemia)
Exudative effusion - Increased vessel permeability, which results in proteins leaking out of tissues and into the pleural space. This can be caused by:
Infection e.g. Pneumonia, TB
Cancer
Inflammatory conditions e.g. RA, SLE
Pulmonary infarct e.g. after PE
Trauma
Other rarer causes:
Hypothyroidism
Meig’s syndrome (Triad of Ascites, Pleural effusion, and Benign ovarian tumour)
Presentation
Patients will present with SOB and Chest pain.
O/E:
Stony dull percussion
Reduced breath sounds
Reduced chest expansion
Tracheal deviation away from the affected side (if large enough)
Investigations
CXR
Management
Conservative if small
Aspiration or Chest drain
Treat underlying cause
Complications
Main complication here is an Empyema (infected pleural effusion). It should be suspected in a patient with improving pneumonia but a new/ongoing fever. Pleural tap should be done and the fluid analysed, which will show pus, low pH, low glucose, and high LDH.

