Pleural Effusion

This is an excessive build up on fluid between the pleura - the space that surrounds the lungs. The area of fluid is clearly visible on an X-ray and usually appears to be white. The fact that it is indeed fluid is shown by the meniscus (curved area) where it meets the sides of the lung. Fluids may include blood or pus. Seeing fluid such as this may indicate infection.

Symptoms such as coughing, shortness of breath, chest pain can often be observed.

Treatment includes removing the fluid, preventing the fluid from building up again and treating the underlying cause (e.g. leakage, lung injury, inflammation).

It’s Trilobite Tuesday! Why is a trilobite called a trilobite? It’s NOT, as people might think, because these ancient arthropods have a cephalon (head), body (thorax) and tail (pygidium). Rather, it’s because their bodies are divided into three lateral sections–the left pleural lobe, axial lobe and right pleural lobe. Those can be easily seen on this large Odontocephalus ageria from the Devonian of Pennsylvania.

Learn much more about trilobites!

Causes of Pleural Effusion: transudates and exudates

We perform an aspirate of the pleural fluid to investigate the cause of pleural effusion.

Transudate ( Exudate (>30g/L protein, fluid LDH:serum LDH ratio >0.6): pneumonia, lung carcinoma, pulmonary infarct, TB, connective tissue disease

Source - Stather et al. Complete SAQs for Medical Finals. 2010. Wiley-Blackwell publishing.

Pleural effusions


  • protein and LDH decreased.
  • CHF
  • Cirrhosis
  • Nephrotic syndrome
  • Peritoneal dialysis
  • Constrictive pericarditis


  • protein and LDH increased.
  • Malignancy
  • TB
  • Pulmonary infection
  • SLE
  • RA
  • Dressler
  • Pancreatitis
  • Trauma

Source = The Requisites, Vascular and Interventional Radiology, Kaufman and Lee