FFinalistSouthampton · 2027
Respiratory
AKT · Respiratory/Pleura

Pleural effusion

Fluid in the pleural space — transudate (systemic) vs exudate (local) by Light's criteria

Overview

Accumulation of fluid in the pleural space. The fundamental split is transudate (low protein — heart/liver/renal failure, hypoalbuminaemia) vs exudate (high protein — infection, malignancy, PE, inflammation), separated by Light's criteria. Diagnostic aspiration (with pleural fluid analysis) is the key step; a purulent/low-pH effusion is an empyema needing a drain.

Recognise

  • Breathlessness, pleuritic pain; STONY DULL percussion, reduced breath sounds and reduced vocal resonance over the effusion; tracheal deviation away if large
  • CXR: blunting of the costophrenic angle, meniscus; ultrasound guides aspiration and detects loculations
  • Transudate (30 g/L): infection, malignancy, PE, inflammation

Red flags

  • Empyema (purulent fluid, pH <7.2, low glucose) → chest drain (see empyema/abscess)
  • Massive effusion with respiratory compromise → therapeutic drainage; haemothorax/malignant effusion → specific management

Differentials & how to tell them apart

Transudatelow protein — bilateral, with heart/liver/renal failure or low albumin; treat the systemic cause
Exudatehigh protein — infection (parapneumonic/empyema), malignancy, PE, inflammation; needs the local cause found
Empyema / haemothorax / chylothoraxpus / blood (haematocrit) / chyle (triglycerides) on aspiration
Pleural effusion — blunting of the costophrenic angle with a meniscus (chest X-ray)

Pleural effusion — blunting of the costophrenic angle with a meniscus (chest X-ray)

InvictaHOG / Public domain — Wikimedia Commons

Investigations

CXR + ULTRASOUND; diagnostic pleural ASPIRATION — protein, LDH (Light's criteria), pH, glucose, cytology, microscopy/culture; LIGHT'S CRITERIA for borderline protein (exudate if fluid:serum protein >0.5, fluid:serum LDH >0.6, or fluid LDH >⅔ upper normal serum); CT/pleural biopsy for suspected malignancy.

Management

Aspirate + Light's criteria → treat the cause; drain symptomatic/empyema/malignant effusions

  1. 1Confirm clinically (stony dull base) and on CXR/ultrasound, then perform a diagnostic pleural aspiration. Apply Light's criteria to classify transudate vs exudate when protein is borderline.Gate: Transudates (heart/liver/renal failure) are treated by addressing the systemic cause — not routinely drained; a purulent/low-pH (<7.2) parapneumonic effusion is an empyema needing a chest drain.
  2. 2Exudates need the local cause found (malignancy → cytology/CT/biopsy; infection → drain); therapeutic/large effusions → controlled drainage; malignant effusions → pleurodesis or indwelling catheter.
Treat the underlying cause — transudates → treat heart/liver/renal failure (don't routinely drain); exudates → treat the local cause
Therapeutic drainage for symptomatic/large effusions — controlled drainage to relieve breathlessness
Empyema → chest drain + antibiotics — purulent/low-pH parapneumonic effusion
Malignant effusion → drainage ± pleurodesis / indwelling pleural catheter — plus treat the cancer

Key points

Stony dull base + reduced breath sounds = pleural effusion → ultrasound-guided aspiration + LIGHT'S CRITERIA (transudate 30 g/L). Transudate (heart/liver/renal) → treat the cause, don't routinely drain; exudate → find the local cause; pus/pH <7.2 = empyema → chest drain.

Monitor & prognosis

Resolution/recurrence, the underlying cause; cytology/biopsy results for malignancy.

Depends on the cause; malignant effusions recur (pleurodesis/catheter help).

Source: BTS pleural disease