Table 2.
Different stages in the evolution of an infected pleural effusion with associated pathological changes and pleural fluid findings.
| Phase | Pathology | Pleural fluid findings |
|---|---|---|
| Exudative | Increased permeability of vascular and visceral pleural membranes VEGF | Nonviscous |
| Free flowing | ||
| Readily drained | ||
| Pleural fluid Cx negative | ||
|
| ||
| Fibrinopurulent | Fibrin deposition on visceral pleura Locules formation IL-8, TNF-α | pH > 7.20 |
| Glucose within normal ranges | ||
| LDH < 3 times ULN | ||
| Viscous | ||
| More viscous | ||
| Pleural fluid cx positive | ||
| Typical “complicated” effusion | ||
|
| ||
| Organizing | Fibroblast entry Pleural peel TGF-β |
Thick pus |
| Very viscous | ||
| pH < 7.20 | ||
| Glucose < 40 | ||
| LDH > 3 times ULN | ||
LDH: lactate dehydrogenase.
ULN: upper limits of normal.
VEGF: vascular endothelial growth factor.
IL-8: interleukin 8.
TNF-α: tumor necrosis factor-alpha.
TGF-β: transforming growth factor-beta.