Pleural effusion and Light's criteria

What it is

A pleural effusion is either transudative or exudative, and the rest of the work follows that split. A transudative effusion comes from an imbalance between hydrostatic and oncotic pressures, raised capillary hydrostatic pressure, that is increased capillary wedge pressure, with a fall in capillary oncotic pressure, which increases fluid movement across the capillaries into the visceral pleura and the pleural space. An exudative effusion comes from pleural and lung inflammation with increased capillary and pleural membrane permeability. Transudative fluid requires no further intervention except treatment directed at the underlying disease, while exudative effusions require more extensive diagnostic investigation.

Causes and risk

Common causes of a transudative effusion are congestive heart failure and low protein states. Common causes of an exudative effusion are pulmonary infections, malignancy of pulmonary or metastatic origin, inflammatory conditions such as pancreatitis and autoimmune diseases, injury such as hemothorax and chylothorax, and pulmonary embolism.

How it presents

The characteristic symptoms are dyspnea, pleuritic chest pain and a dry, nonproductive cough, together with symptoms of the underlying disease, such as fever in pneumonia or dyspnea in left-sided heart failure.

Physical exam findings:

• Inspection and palpation: asymmetric expansion and reduced tactile fremitus.
• Auscultation: faint or absent breath sounds, and a pleural friction rub.
• Percussion: dullness over the area of effusion.