Pleural effusion

What is Pleural effusion?

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A pleural effusion is a disease of the lung.The pleura are thin films of connective tissue, which line both the outer surface of the lungs, and the inside of the chest cavity. The relationship of the pleura to the lungs and chest can be imagined as if the pleura were a balloon blown up inside the chest, into which the lungs have been pushed. Thus, there are in fact two layers of pleura between the outer surface of the lung and the chest wall. One is adherent to the lung, whereas the other layer follows the outline of the chest wall. The two layers press up against one another, and in the healthy chest, there is no air or significant fluid between them. In a pleural effusion, fluid is present in this potential space between the two layers of pleura.

This does not include pus in the pleural space (empyema) or blood (haemothorax).

Statistics on Pleural effusion?

Pleural effusions are a very common phenomena, since they can be caused by any of a number of lung and heart disorders. A small pleural effusion is often present on a chest x-ray when somebody has a significant heart or lung problem.

Risk Factors for Pleural effusion

The following diseases may cause pleural effusion:

Heart failure
Bacterial pneumonia
lung cancer and other tumours with lung metastases
Pulmonary embolism
Radiation therapy to the chest
Nephrotic syndrome
Hypothyroidism
Ovarian tumours
Tuberculosis
Connective tissue disease (for example, rheumatoid arthritis, lupus)
Rarely: heart attack, acute pancreatitis, mesothelioma, sarcoidosis, yellow-nail syndrome, familial Mediterranean fever.

Progression of Pleural effusion

The natural history of pleural effusions is largely determined by the cause. Pleural effusions as a result of a transient cause (e.g. pneumonia, infarction, exacerbation of heart failure) will reasorb. However if the cause is progressive (eg. mesothelioma or pulmonary metastases), then the effusion, even if drained will re-accumulate.Large effusions will cause shortness of breath since they preclude the lung on that side from expanding adequately - they are often accompanied by a degree of collapse.

How is Pleural effusion Diagnosed?

Chest x-ray can detect pleural effusion containing 300ml or more.

Pleural effusions can be unilateral or bilateral - a large unilateral pleural effusion is more ominous since it can signify a malignancy.

Diagnostic thoracentesis is a simple procedure involving sampling of the pleural fluid for analysis. It may be used to give clues to the cause of the effusion.

Prognosis of Pleural effusion

Massive effusion may be life threatening. Otherwise, the prognosis clearly depends on the underlying cause of effusion. Malignant pleural effusion may be recurrent.

How is Pleural effusion Treated?

Large pleural effusions, causing severe breathlessness, are drained, by needle in an acute emergency, or otherwise by chest drain inserted under local anaesthetic.

Malignant pleural effusions may be recurrent. They are treated by drainage, followed by the instillation of certain chemicals into the pleural space which help stick the two layers of pleura together, as to stop further fluid accumulating.

Other effusions are treated by treating the underlying cause.

Pleural effusion References

Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison's Principles of Internal Medicine. 16th Edition. McGraw-Hill. 2005.
Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999. pp749-751
Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 1998. p825

Talley NJ, O'Connor S. Clinical examination. Third Ed. MacClennan & Petty, 1996. p120