Diseases of the pleura (pneumothorax, pleurisy, pleural effusion) – etiology, pathogenesis, and clinical manifestations.
I. Pneumothorax
Air accumulation in the pleural cavity, leading to lung collapse.
Etiology
Spontaneous
- Primary: young, tall, thin males, rupture of subpleural blebs.
- Secondary: underlying lung disease (COPD, tuberculosis, cystic fibrosis).
Traumatic
- Penetrating or blunt chest trauma.
- Iatrogenic: central line placement, mechanical ventilation.
Tension pneumothorax
- One-way valve mechanism → air enters but cannot exit → intrathoracic pressure rises.
Pathogenesis
- Air enters pleural space → loss of negative pressure → partial or complete lung collapse.
- In tension type → mediastinal shift → compression of opposite lung and large veins → severe hemodynamic compromise.
Clinical manifestations
- Sudden, sharp pleuritic chest pain.
- Dyspnea.
- Hyperresonant percussion.
- Decreased or absent breath sounds on affected side.
- In tension pneumothorax: hypotension, distended neck veins, tracheal deviation away from affected side → medical emergency.
II. Pleurisy (pleuritis)
Definition
Inflammation of the pleural layers, often with fibrinous exudate.
Etiology
- Viral infections (most common).
- Bacterial pneumonia or tuberculosis.
- Pulmonary embolism (infarction-related).
- Autoimmune diseases (SLE, rheumatoid arthritis).
Pathogenesis
- Inflammatory process → pleural surface irritation.
- Fibrin deposition → roughened pleural surfaces → friction during breathing.
Clinical manifestations
- Sharp, localized chest pain, worsens with deep inspiration or coughing.
- Pain often referred to shoulder or neck (phrenic nerve irritation).
- Pleural friction rub on auscultation (coarse, grating sound).
III. Pleural effusion
Definition
Excess fluid accumulation in the pleural space.
Etiology
Transudative effusion
- Increased hydrostatic pressure: heart failure.
- Decreased oncotic pressure: nephrotic syndrome, liver cirrhosis.
Exudative effusion
- Infections: pneumonia (parapneumonic), TB.
- Malignancy.
- Pulmonary embolism.
- Autoimmune diseases.
Pathogenesis
- Imbalance in fluid formation and absorption → fluid accumulation.
- Lung compression → reduced ventilation → dyspnea.
Clinical manifestations
- Dyspnea (due to lung compression).
- Dullness to percussion over fluid area.
- Decreased or absent breath sounds.
- Reduced chest expansion on affected side.
- Egophony (E-to-A change) and diminished tactile fremitus above fluid level.