Definition
Inflammation of the pleura (membranes surrounding the lungs). Also known as pleurisy.
Classification
- Fibrinous (dry) – No fluid; just fibrin deposits on pleural surface (due to inflammation but without exudate yet)
- Exudative (wet) – With pleural effusion:
- Serofibrinous – clear/yellow fluid with fibrin
- Purulent – pus due to bacterial infection
- Putrid – foul-smelling fluid from necrotic infection
- Hemorrhagic – bloody fluid from malignancy, TB, or trauma
Etiology
Pleuritis is usually secondary to another underlying cause.
- Viral infections (e.g., Coxsackie B, RSV, CMV, adenovirus, influenza) – Most common cause; viruses directly irritate pleura.
- Pneumonia – Inflammation spreads from lung parenchyma to pleura.
- Tuberculosis (TB) – Causes granulomatous inflammation and fibrin-rich effusion.
- Cancer – Direct invasion or metastasis to pleura leads to hemorrhagic effusion.
- Pulmonary embolism – Infarction can irritate pleura causing inflammation.
- Collagen diseases (e.g., lupus, RA) – Autoimmune pleuritis with lymphocyte-rich fluid.
- Trauma – Rib fractures or injury irritate the pleura.
- Pancreatitis – Inflammatory enzymes can reach diaphragm and pleura.
- Uremia – Toxins in blood due to kidney failure irritate pleura.
Special effusion types:
- Hydrothorax – Transudate (low protein, low SG); caused by R heart failure, nephrotic syndrome, liver cirrhosis.
- Hemothorax – Blood in pleura, usually from trauma or broken ribs.
- Chylothorax – Lymph accumulation due to thoracic duct damage.
- Empyema – Pus in pleural cavity from ruptured lung abscess.