Preparatory Mindset
Pleural disease is a high-yield, pattern-recognition topic. The core exam skill is the transudate vs exudate distinction (Light's criteria / Rivalta test) — because it instantly narrows the differential: transudate = hydrostatic/oncotic imbalance (heart failure, cirrhosis, nephrotic syndrome); exudate = inflammation/malignancy (parapneumonic, tuberculosis, malignancy, SLE). The classic vignette is a young man with sudden pleuritic chest pain and a unilateral effusion + fever + lymphocytic fluid → tuberculous pleuritis (common in HK/China). Pneumothorax then splits into primary (tall thin young smoker, apical blebs) vs secondary (any lung disease; ≥50 y with significant smoking counts as secondary) — with a clear BTS-based management ladder: conservative → aspiration → chest drain, and pleurodesis indications that are routinely tested.
Core Concepts
Pleural effusion — definition & physiology
- Pleural effusion = abnormal accumulation of fluid in the pleural space (16CM exam tested).
- Small effusions (<0.3–0.5 L) may be clinically silent; larger volumes compress the lung.
Transudate vs exudate
| Transudate | Exudate | |
|---|---|---|
| Mechanism | ↑ hydrostatic / ↓ oncotic pressure (no pleural disease) | Pleural surface inflammation/malignancy (capillary leak) |
| Protein (fluid/serum) | <0.5 | >0.5 |
| LDH (fluid/serum) | <0.6 | >0.6 |
| LDH absolute | <200 IU/L | >200 IU/L (teacher criteria) |
| Rivalta test | Negative | Positive (protein-precipitation test, classic in Chinese curricula) |
| Causes | Heart failure, cirrhosis (hepatic hydrothorax), nephrotic syndrome, hypothyroidism, PE (exudate more common) | Parapneumonic/empyema, tuberculosis, malignancy (mesothelioma, lung/breast), SLE/RA, PE, pancreatitis |
Special fluid analyses:
- Chylothorax: cloudy, triglyceride >1.21 mmol/L (Sudan III red staining), normal cholesterol — thoracic duct rupture (trauma, lymphoma).
- Pseudochylothorax: light yellow/brown, cholesterol crystals (cholesterol >5.18 mmol/L, lymphocytes, RBCs) — chronic exudates (TB, RA).
- Low glucose <3.3 mmol/L: pyothorax/empyema, SLE, TB, malignant effusion.
- Tuberculous pleurisy: lymphocytic exudate; MTB smear-positive rate only ~10% (culture/pleural biopsy improves yield).
Aetiology & clinical features
- Causes by mechanism: infection (pneumonia, lung abscess, bronchiectasis → parapneumonic/empyema), tumour, TB, cardiac (HF), renal/hepatic (transudate), autoimmune (SLE, RA).
- Symptoms: dyspnoea (most common — large effusion), pleuritic chest pain, cough; constitutional symptoms if TB/malignancy.
- Signs: decreased breath sounds, dullness to percussion, reduced tactile fremitus, stony dullness; mediastinal shift away from the effusion if massive.
Diagnosis
- CXR: blunted costophrenic angle (≥300 mL visible); fluid meniscus.
- Pleural tap (diagnostic thoracentesis): contraindicated in pyothorax with hemorrhagic tendency; bedside USG guidance improves success and reduces complications (HKHA). Send: protein, LDH, glucose, cell count & differential (lymphocytic → TB/malignancy; neutrophilic → parapneumonic), cytology, AFB smear/culture, pH.
- Rivalta test (protein precipitation) for exudate screening; Light's criteria for definitive classification.
Treatment
- Treat the underlying cause (HF → diuretics; parapneumonic → antibiotics ± drainage).
- Therapeutic drainage for symptomatic large effusions; chest drain for empyema/pyothorax (with pleural irrigation using 2% NaHCO₃ or normal saline repeatedly per Chinese teaching); consider fibrinolytics/surgery for loculated empyema.
- Tuberculous pleuritis → full anti-TB regimen (see TB chapter).
- Malignant effusion → drainage + pleurodesis (talc) / indwelling catheter.
Pneumothorax
- Asymptomatic → conservative (observation + O₂); chest drain if enlarging/worsening. - Symptomatic without high-risk features, insufficient size → conservative. - Symptomatic without high-risk features, sufficient size → conservative + monitor, OR needle aspiration / chest drain. - Symptomatic and/or high-risk with sufficient size → chest drain insertion (tension = immediate needle decompression then drain).
- Definition: air in the pleural space without trauma or iatrogenic intervention.
- Primary spontaneous (PSP): no underlying lung disease — typical tall thin young smoker; apical blebs found in ~85%.
- Secondary spontaneous (SSP): underlying lung disease (COPD, TB, malignancy, cystic fibrosis); ≥50 y with significant smoking history is managed as SSP.
- Size: "sufficient" = ≥2 cm laterally/apically on CXR (or any size on CT safely accessible).
- High-risk characteristics: haemodynamic compromise (tension pneumothorax), significant hypoxia, bilateral pneumothorax, underlying lung disease, age ≥50 + smoking, haemopneumothorax.
- Management (BTS 2023):
- Indications for surgical pleurodesis (VATS) (high-yield list): first pneumothorax with tension, or first secondary with significant physiological compromise; second ipsilateral; first contralateral; synchronous bilateral; spontaneous haemothorax; persistent air leak (>5–7 days of drainage) or failed re-expansion; professions at risk (pilots, divers); pregnancy. Chemical pleurodesis (talc, minocycline) if unfit/refuse surgery.
- Chest-drain technique (Chinese teaching): local anaesthesia (1% lidocaine to skin and rib), horizontal 2–3 cm incision, underwater seal ± suction (−20 cm H₂O); tube placed 1–2 cm below water surface keeping intrapleural pressure −1 to −2 cm H₂O.
HKHA Handbook (LMCHK) — Key Points
- Pleural effusion (BTS 2023): do not tap bilateral effusions when the clinical picture strongly suggests transudate, unless atypical features or failure to respond to therapy; diagnostic tapping with bedside ultrasound guidance improves success and reduces complications. Procedures: pleural aspiration (Pr 17), pleural biopsy (Pr 18), chest drain insertion (Pr 19).
- Spontaneous pneumothorax (BTS 2023): size threshold for intervention ~≥2 cm laterally/apically on CXR; manage by symptoms ± high-risk characteristics (tension, hypoxia, bilateral, underlying lung disease, ≥50 y + significant smoking, haemopneumothorax); tension → immediate decompression; pleurodesis indications as listed above (2nd ipsilateral, 1st contralateral, synchronous bilateral, persistent air leak >5–7 days, pilots/divers, pregnancy).
- No dedicated handbook chapter for empyema — follow CAP/HAP guidance for the underlying infection and drain the pleural space; consult ID/respiratory teams.
High-Yield Points
- Exudate: fluid/serum protein >0.5, LDH >0.6, LDH >200 IU/L, Rivalta (+); transudate: HF/cirrhosis/nephrotic.
- Chylothorax: triglyceride >1.21 mmol/L, thoracic duct rupture; pseudochylothorax: cholesterol crystals.
- Low-glucose effusion: pyothorax, SLE, TB, malignancy.
- TB pleurisy: lymphocytic; smear ~10% positive.
- PSP: tall thin young smoker, apical blebs 85%; SSP if ≥50 y + significant smoking.
- Sufficient size ≥2 cm; tension → immediate decompression.
- Pleurodesis: 2nd ipsilateral, 1st contralateral, synchronous bilateral, persistent leak >5–7 days, pilots/divers, pregnancy.
Topic Summary
Pleural disease hinges on the transudate/exudate dichotomy (Light's criteria, Rivalta) and the tension between hydrostatic causes (HF, cirrhosis, nephrotic) and inflammatory/malignant causes (parapneumonic, TB, malignancy, SLE). Diagnosis is USG-guided tap with fluid analysis (protein, LDH, glucose, cytology, AFB); treatment targets the cause plus drainage for symptomatic/empyema cases. Spontaneous pneumothorax is managed conservatively for asymptomatic small PSP, with needle aspiration or chest drain for symptomatic/sufficient-size cases, chest drain for high-risk/SSP, and surgery/pleurodesis for recurrent, tension, bilateral, or persistent-leak scenarios — the BTS-2023-based management ladder being an LMCHK priority.