40. Spontaneous pneumothorax, pleural empyema and pleural metastases

1. Definition

• Spontaneous pneumothorax → air in the pleural space without trauma, with collapse of the lung
  • Primary → no known lung disease
  • Secondary → underlying lung disease
• Pleural empyema → pus in the pleural space, or fluid with organisms on Gram stain or culture
• Pleural metastases → secondary tumour deposits on the pleura, usually with a malignant pleural effusion (MPE)

2. Epidemiology

• Primary spontaneous pneumothorax → tall, thin young men, 15–35 years; smokers; right side more often; bilateral in < 10%
• Secondary → age > 50 years; COPD most common cause
• Recurrence after a first primary pneumothorax → about 30%, mostly within 1 year
• Empyema → most follow pneumonia; 1 in 5 die or need surgery
• MPE → about 15% of patients with cancer; median survival about 5 months

3. Aetiology and risk factors

Spontaneous pneumothorax

• Primary → rupture of apical subpleural blebs (< 2 cm) or bullae; smoking (risk × 10–20), tall stature, Marfan's syndrome
• Secondary:
  • COPD, bullous emphysema
  • Cystic fibrosis (10% develop one)
  • Asthma, interstitial lung disease
  • Infection → Pneumocystis (HIV), tuberculosis, necrotising pneumonia
  • Lung cancer, sarcoma metastases
  • Catamenial → endometriosis; women 20–30 years, 2–3 days after menstruation starts, right side
  • Lymphangioleiomyomatosis, Ehlers-Danlos syndrome

Empyema

• Parapneumonic → about 60%
• Postoperative → lung resection, oesophagectomy, bronchopleural fistula
• Trauma → haemothorax, penetrating injury
• Oesophageal perforation
• Subphrenic or liver abscess
• Ruptured lung abscess
• Organisms → Streptococcus pneumoniae, Streptococcus anginosus (milleri), S. aureus, anaerobes, Gram-negatives; tuberculosis

Pleural metastases

• Lung and breast cancer → about 75% of MPEs
• Lymphoma, ovary, stomach, unknown primary
• Primary pleural tumour → malignant mesothelioma (asbestos, latency 15–40 years)

4. Pathogenesis

Pneumothorax

1. Bleb ruptures
2. Air enters the pleural space → lung collapses
3. One-way valve → tension pneumothorax → mediastinal shift, reduced venous return, cardiac arrest

Empyema stages

1. Exudative (stage I) → 2–5 days after pneumonia; thin fluid, low cell count, normal pH and glucose; antibiotics alone may cure
2. Fibrinopurulent (stage II) → 5–14 days; turbid fluid, fibrin, loculations; pH < 7.2, low glucose, high lactate dehydrogenase (LDH); needs drainage
3. Organising (stage III) → after 2–6 weeks; thick fibrous peel → trapped lung; needs decortication

MPE

1. Tumour cells seed the pleura
2. Increased capillary permeability, blocked lymphatic drainage
3. Exudate accumulates → recurs after drainage

5. Classification

Pneumothorax

• By cause → primary spontaneous, secondary spontaneous, traumatic, iatrogenic (central line, lung biopsy, ventilation)
• By size (British Thoracic Society, BTS) → large if rim ≥ 2 cm at the hilum level on chest X-ray (≥ 2 cm ≈ 50% volume)
• American → large if ≥ 3 cm at the apex
• By physiology → simple, tension

Pleural effusion (Light's criteria)

• Exudate if any one:
  1. Pleural fluid to serum protein ratio > 0.5
  2. Pleural fluid to serum LDH ratio > 0.6
  3. Pleural fluid LDH > 2/3 of the upper limit of normal serum LDH
• Transudate → heart failure, cirrhosis, nephrotic syndrome, hypothyroidism
• Exudate → infection, cancer, pulmonary embolism, pancreatitis, rheumatoid arthritis, tuberculosis

6. Clinical picture

Symptoms

• Pneumothorax → sudden pleuritic chest pain and dyspnoea, often at rest; secondary → severe dyspnoea with small pneumothorax
• Empyema → persistent fever after pneumonia, rigors, weight loss, pleuritic pain, malaise
• MPE → progressive dyspnoea, cough, chest heaviness, weight loss

Signs

• Pneumothorax:
  • Reduced expansion
  • Hyper-resonant percussion
  • Absent breath sounds
  • Subcutaneous emphysema
• Tension → tachycardia, hypotension, tracheal deviation away, distended neck veins, hypoxia
• Effusion or empyema → stony dull percussion, absent breath sounds, reduced vocal resonance
• Chronic empyema → clubbing, chest wall sinus (empyema necessitans)
• Mesothelioma → chest wall mass, contracted hemithorax

7. Diagnosis

Imaging

• Erect posteroanterior chest X-ray → visible pleural line, no lung markings beyond it
• CT → small or uncertain pneumothorax, bullous disease, blebs before surgery
• Lung ultrasound → no "lung sliding", lung point
• Effusion → blunted costophrenic angle, meniscus
• Ultrasound → effusion size, septations, guides aspiration; all pleural procedures under ultrasound
• Contrast CT → empyema: "split pleura" sign (enhancing thickened pleura); pleural nodules in metastases; underlying tumour

Laboratory

• Diagnostic pleural aspiration:
  • Appearance → pus, blood, milky (chyle)
  • pH → < 7.2 in a parapneumonic effusion → chest drain
  • Glucose low, LDH high → infection, rheumatoid, cancer
  • Protein and LDH → Light's criteria
  • Gram stain, culture, acid-fast bacilli
  • Cytology → positive in about 60% of MPE
• Pleural biopsy → thoracoscopic (VATS) or local anaesthetic thoracoscopy; CT-guided biopsy; mesothelioma needs histology

8. Differential diagnosis

• Pneumothorax → large bulla (CT shows lung around it), myocardial infarction, pulmonary embolism, pericarditis
• Empyema → lung abscess, simple parapneumonic effusion, subphrenic abscess
• MPE → heart failure, tuberculous effusion, pulmonary embolism, mesothelioma

9. Treatment

Conservative: pneumothorax (BTS 2023)

• Tension → immediate needle decompression (2nd intercostal space mid-clavicular line, or 4th–5th space in the mid-axillary line), then chest drain
• High-risk features → chest drain:
  • Haemodynamic instability
  • Significant hypoxia
  • Bilateral pneumothorax
  • Underlying lung disease
  • Age ≥ 50 years with significant smoking history
  • Haemothorax
• Primary, minimal symptoms → conservative, regardless of size; review in 2–4 days
• Primary, symptomatic → needle aspiration, ambulatory device (one-way valve), or chest drain
• Secondary → chest drain usually; admit
• Oxygen → speeds reabsorption (four times faster)
• No flying until resolved on chest X-ray; no diving for life unless pleurectomy
• Stop smoking

Surgical: pneumothorax

• Indications:
  • Second ipsilateral pneumothorax
  • First contralateral pneumothorax
  • Persistent air leak > 3–5 days or failure to re-expand
  • Bilateral simultaneous
  • Haemopneumothorax
  • High-risk occupations → pilots, divers
  • Previous tension pneumothorax
• Operation → VATS bullectomy/blebectomy + pleurodesis (parietal pleurectomy or pleural abrasion)
• Recurrence → about 1–2% after open pleurectomy, about 5% after VATS, 5–10% after chemical pleurodesis alone
• Unfit → talc slurry or autologous blood patch via the drain

Conservative: empyema

• IV antibiotics → cover anaerobes (co-amoxiclav, or cefuroxime + metronidazole); 2–6 weeks
• Chest drain under ultrasound for pus, pH < 7.2, positive Gram stain or culture
• Loculated → intrapleural tissue plasminogen activator (tPA) + DNase (MIST2)
• Nutrition, physiotherapy, thromboprophylaxis

Surgical: empyema

• Failure to improve after 5–7 days of drain and antibiotics
• VATS debridement and decortication → stage II, early stage III
• Open decortication → stage III, thick peel, trapped lung
• Unfit → open drainage, rib resection, Eloesser flap (open window)
• Bronchopleural fistula → closure, muscle flap

Pleural metastases and MPE

• Aim → relief of dyspnoea; not curative
• Therapeutic aspiration → symptom relief; ≤ 1.5 L at a time (re-expansion pulmonary oedema)
• Recurrent MPE, lung expands → talc pleurodesis (slurry via drain, or poudrage at thoracoscopy)
• Trapped lung or failed pleurodesis → indwelling pleural catheter (IPC), drained at home
• Treat the primary → chemotherapy, endocrine, targeted therapy
• Mesothelioma → chemotherapy, immunotherapy; radical surgery (extended pleurectomy and decortication) only in selected epithelioid disease

10. Complications

• Pneumothorax:
  • Tension pneumothorax
  • Recurrence
  • Persistent air leak, bronchopleural fistula
  • Haemopneumothorax
  • Re-expansion pulmonary oedema → large, long-standing collapse drained fast
  • Surgical emphysema, pneumomediastinum
• Empyema:
  • Trapped lung, fibrothorax, restrictive lung function
  • Bronchopleural fistula
  • Empyema necessitans (through the chest wall)
  • Sepsis, death
• MPE → recurrence, loculation, catheter infection