In pleural effusion (PE; synonyms: Encapsulated fluid in the lung; Encapsulated pleurisy; Bacterial pleuritis; Bacterial pleuritis exsudativa; Bacterial pleuritis with effusion; Bacterial serous pleuritis; Exudative pleuritis; Pleural effusion; Pleurisy due to pneumococcus; Pleurisy due to streptococcus; Pleuritis exsudativa; Pleurisy with effusion; Pleurorrhea; Serofibrinous pleurisy; Serous pleurisy; ICD-10 J90-: Pleural effusion, not elsewhere classified/J91-: Pleural effusion in diseases classified elsewhere) is a pathological (pathological) increase in the fluid content between the pleura parietalis (pleura) and pleura visceralis (pleura).
Physiologically, there is only a very small amount of fluid (circa 15 ml) between the two sheets. The fluid accumulates in the pleural space when production far exceeds reabsorption (uptake). The lymphatic system is capable of reabsorbing many times the fluid that is normally produced. This process is disturbed only when excessive fluid production occurs.
The pathogenesis (disease development) of pleural effusion depends on the underlying disease. Pleural effusion can be a symptom of many diseases (see under “Differential diagnoses”). The main cause is considered to be congestive heart failure (pump failure), followed by bacterial pneumonia (pneumonia). Note: Because of the multimorbidity of elderly patients, a singular (sole) cause of pleural effusion often cannot be found.
Recurrent malignant pleural effusion secondary to pleural carcinomatosis (involvement of the pleura with metastases from a malignant tumor) is one of the most common findings of malignant disease (see Differential Diagnoses/Neoplasms below).
The fluid can be differentiated according to its components into:
- Blood (hematothorax)
- Pus (lat. pus) (pleural empyema).
- Exudate* – more or less turbid fluid of inflammatory origin; may be purulent, fibrinous, hemorrhagic, serous, etc.
- Lymph (chylothorax).
- Transsudate* – usually serous fluid of non-inflammatory origin that is low in cells and protein.
* Differential diagnosis of exudate and transsudate see below laboratory diagnostics.
Pleural effusion is one of the most common diseases in clinical medicine. In the U.S., approximately 500,000 people per year develop pleural effusion.
Course and prognosis: The prognosis of the disease depends on the underlying disease.