Decision support only — not a substitute for the BTS 2023 pleural guideline, the BTS pleural-procedures statement, or your respiratory team. Two headline shifts in 2023: pneumothorax is now managed by symptoms, not size, with conservative and ambulatory options; and ultrasound should guide every pleural intervention. Excludes mesothelioma (separate guideline). Verify all doses and local pathways.
1 The undiagnosed unilateral effusion
History firstbefore you tap
Clinical context shapes everything.
If a transudate is clinically obvious (e.g. heart failure), treat the cause and only sample if it fails to resolve or features don't fit.
Image & sampleultrasound-guided
Effusion needing characterisation.
Ultrasound-guided aspiration for protein, LDH, pH, glucose, cytology, MC&S. Send paired serum protein & LDH for Light's.
Light's criteriaexudate vs transudate
Borderline serum-fluid gradient.
Exudate if any: fluid/serum protein >0.5, fluid/serum LDH >0.6, or fluid LDH >⅔ upper-normal serum. On diuretics, Light's over-calls exudate — check the protein gradient.
Still undiagnosedexudate, no cause
Exudative effusion, cytology negative.
Contrast CT (pleural phase) + refer for thoracoscopy/image-guided pleural biopsy. Think malignancy, TB, PE.
Order the tests by likelihood: pH <7.2 in an infected effusion mandates drainage (below); low glucose suggests empyema, malignancy, TB, or rheumatoid; lymphocytic exudate → malignancy or TB; very high amylase → pancreatitis or oesophageal rupture; chylous (triglycerides) → thoracic duct. Don't drain large volumes too fast — re-expansion pulmonary oedema.
2 Spontaneous pneumothorax — symptoms, not size
Tensiontreat before imaging
Haemodynamic compromise, tracheal shift, severe distress.
Immediate decompression (large-bore cannula/finger thoracostomy) then chest drain — do not wait for a CXR.
Minimal symptomsPSP, any size
No significant pain/breathlessness, no physiological compromise.
Conservative management can be considered regardless of size (BTS 2023) — observe, analgesia, follow-up.
Symptomatic PSPgood support available
Symptomatic primary spontaneous pneumothorax.
Ambulatory device (e.g. one-way valve) where expertise/follow-up exist; otherwise needle aspiration or small-bore drain.
Secondary (SSP)underlying lung disease
COPD/ILD etc. — less reserve, higher risk.
Lower threshold to drain + admit + oxygen. Refer for surgery (VATS/pleurodesis) for persistent leak or recurrence prevention.
The 2023 shift: a symptoms-based pathway replaces the old size cut-offs. Counsel on no flying until resolved and never diving again after spontaneous pneumothorax. Persistent air leak or second ipsilateral event → surgical referral.
3 Pleural infection & malignant effusion
Pleural infection / empyema
- Drain ifpH <7.2, frank pus, or organisms on Gram stain/culture → prompt chest drain + antibiotics.
- IntrapleuralLoculated/failing drainage → tPA + DNase (MIST-2); surgery if that fails.
- Risk scoreRAPID (renal, age, purulence, infection source, dietary albumin) stratifies outcome RAPID.
- Follow-upCT to exclude occult malignancy if symptoms persist; PET-CT not used here.
Malignant pleural effusion
- AimSymptom control; manage in an MDT with palliative-care input.
- OptionsIndwelling pleural catheter or talc pleurodesis — choice driven by lung re-expansion and patient preference.
- Trapped lungIf the lung won't re-expand, IPC is preferred over pleurodesis.
4 Procedure safety
Don't harm
- UltrasoundUse real-time ultrasound for every pleural intervention — never mark a "safe spot" and tap later.
- Re-expansionDon't drain >~1.5 L in one sitting; stop for cough/chest tightness — re-expansion pulmonary oedema.
- TensionClinical diagnosis — decompress before imaging.
Don't miss
- BilateralBilateral effusions are usually transudative (HF, hypoalbuminaemia) — the unilateral work-up doesn't apply.
- DiureticsTreated HF can push a transudate into "exudate" on Light's — use the protein gradient.
- CytologyA single negative cytology doesn't exclude malignancy — pursue histology.
Sources.
Roberts ME et al. "British Thoracic Society Guideline for pleural disease," Thorax 2023 (undiagnosed unilateral effusion pathway; symptoms-based spontaneous-pneumothorax management with conservative/ambulatory options; pleural infection; malignant effusion). BTS Clinical Statement on Pleural Procedures 2023. Light's criteria (Light et al). eTG.
Key evidence: MIST-2 (intrapleural tPA + DNase for pleural infection); RAPID score (pleural-infection risk stratification); the conservative- and ambulatory-management pneumothorax trials underpinning the 2023 shift.
Caveats: mesothelioma and benign non-infective pleural disease are covered in separate BTS guidance. Conservative pneumothorax management requires reliable follow-up and a suitable patient — not a default for everyone. Light's criteria misclassify a minority; interpret with the clinical picture. Verify all doses and local pathways. Companion to the respiratory set.