Pleural effusion is a buildup of excess fluid in the space between the lungs and the chest wall (pleural space). The two main types of pleural effusion fluid are categorized based on their characteristics and underlying causes:
1. Transudative Pleural Effusion
This type of pleural effusion is similar to the fluid normally found in a healthy pleural space. It results from a fluid leak across the normal pleura, often due to increased pressure in the blood vessels or low levels of blood protein. [Source: Penn Medicine, Cleveland Clinic, St. Vincent's Lung Health, WebMD, Canadian Cancer Society]
- Causes: Increased blood pressure within blood vessels (hydrostatic pressure), low blood protein levels (hypoproteinemia) leading to decreased osmotic pressure.
- Characteristics: Low protein content, clear, watery fluid.
2. Exudative Pleural Effusion
Exudative pleural effusion arises from inflammation or damage to the pleura itself. This type of effusion contains a higher protein level than transudative fluid and often has other cells and substances in it. [Source: Penn Medicine, WebMD, NHLBI]
- Causes: Various conditions including infections (pneumonia, tuberculosis), cancers (lung, breast), autoimmune diseases (rheumatoid arthritis, lupus), pancreatitis, pulmonary embolism.
- Characteristics: Higher protein content, may be cloudy or purulent, contains inflammatory cells.
Further subtypes of exudative effusions exist, depending on the specific cause, but the transudative/exudative classification is the most fundamental distinction. [Source: Biomedical Central] A thorough pleural fluid analysis is essential for determining the specific type and underlying cause of the pleural effusion. [Source: MedlinePlus]
