Key Facts

A pleural effusion is an abnormal collection of fluid in the pleural space between the visceral and parietal pleura. It is classified as transudative or exudative based on the biochemical analysis of the pleural fluid.

Epidemiology

• ~1 million cases per year in the UK
• Heart failure is the commonest cause overall
• Parapneumonic effusion/empyema: ~65,000 cases per year in UK
• Malignant effusion: affects ~50% of patients with metastatic cancer

Aetiology

Transudative (protein <25 g/L):

• Heart failure (most common)
• Liver cirrhosis (hepatic hydrothorax)
• Nephrotic syndrome
• Hypothyroidism
• Meigs syndrome (ovarian fibroma + effusion + ascites)
• Peritoneal dialysis

Exudative (protein >35 g/L):

• Parapneumonic effusion/empyema
• Malignancy (lung, breast, lymphoma, mesothelioma)
• Tuberculosis
• Pulmonary embolism
• Autoimmune (RA, SLE)
• Pancreatitis (typically left-sided, high amylase)
• Drug-induced

Pathophysiology

• Normal pleural fluid: ~0.1-0.2 mL/kg, produced by systemic capillaries in parietal pleura, absorbed by parietal pleural lymphatics
• Transudates: imbalance of hydrostatic/oncotic pressures (elevated capillary hydrostatic pressure or reduced plasma oncotic pressure)
• Exudates: increased capillary permeability due to inflammation, infection, or malignancy; impaired lymphatic drainage

Typical Presentation

• Progressive breathlessness (proportional to effusion size)
• Pleuritic chest pain (if inflammatory cause)
• Dry cough
• Reduced exercise tolerance

Clinical Signs

• Reduced chest expansion on affected side
• Stony dull percussion note
• Reduced/absent breath sounds
• Reduced tactile vocal fremitus
• Mediastinal shift away from large effusion
• Tracheal deviation (towards in collapse, away in effusion)

Features Suggesting Cause

• Bilateral + oedema: heart failure
• Fever + pleuritic pain: infection (empyema)
• Weight loss + cachexia: malignancy
• Rheumatoid nodules + joint disease: RA
• Night sweats + weight loss: TB

Red Flags

• Rapidly accumulating effusion
• Bloodstained fluid on aspiration
• Loculated effusion with sepsis (empyema)
• Massive effusion causing mediastinal shift
• Non-resolving effusion despite treatment of presumed cause

Bedside

• Chest X-ray: blunting of costophrenic angle (>200mL on PA film), meniscus sign, opacification
• Thoracic USS: gold standard for detecting and guiding aspiration; identifies loculations, pleural thickening
• Pulse oximetry: baseline

Bloods

• FBC, CRP: infection markers
• U&Es: renal function
• LFTs, albumin: liver disease, protein status
• BNP/NT-proBNP: heart failure
• Coagulation: pre-aspiration

Pleural Fluid Analysis (BTS-recommended)

• Appearance: clear/straw (transudate), turbid (empyema), bloodstained (malignancy/trauma), milky (chylothorax)
• Protein: transudate <25 g/L, exudate >35 g/L; if 25-35 g/L use Light's criteria
• LDH: elevated in exudates
• pH: <7.2 suggests empyema (requires chest drain) or RA
• Glucose: low in empyema (<2.2), RA, TB, malignancy
• MC&S: bacterial infection
• Cytology: malignant cells (~60% sensitivity for malignancy)
• Cell differential: neutrophils (parapneumonic), lymphocytes (TB, malignancy, RA)
• Amylase: elevated in pancreatitis, oesophageal rupture
• Triglycerides: >1.24 mmol/L indicates chylothorax
• Adenosine deaminase (ADA): elevated >40 U/L supports TB

Imaging

• CT chest (contrast): pleural thickening, masses, lung parenchyma, lymphadenopathy
• PET-CT: if malignancy suspected

Special Tests

• Pleural biopsy: thoracoscopic (VATS) biopsy — gold standard for undiagnosed exudative effusions (sensitivity >90% for mesothelioma/TB)
• CT-guided biopsy: alternative
• Bronchoscopy: if endobronchial lesion suspected

Non-pharmacological

• Treat underlying cause (diuretics for heart failure, antibiotics for infection)
• USS-guided aspiration for symptomatic relief (drain max 1.5L at one time to avoid re-expansion pulmonary oedema)

Pharmacological

• Heart failure: diuretics (furosemide 40-80mg PO/IV), salt/fluid restriction
• Parapneumonic/empyema: antibiotics (co-amoxiclav/piperacillin-tazobactam) + chest drain if pH <7.2
• TB pleuritis: standard anti-TB therapy (RIPE: rifampicin, isoniazid, pyrazinamide, ethambutol)
• Malignant effusion: talc pleurodesis or indwelling pleural catheter (IPC) for symptom control
• Intrapleural fibrinolytics: alteplase 10mg + DNase 5mg BD via chest drain for loculated empyema (MIST2 trial)

Surgical/Interventional

• Therapeutic aspiration: USS-guided; for symptom relief
• Intercostal chest drain: empyema (pH <7.2), large symptomatic effusion, haemothorax
• Talc pleurodesis: via chest drain (slurry) or thoracoscopy (poudrage) for recurrent malignant effusion
• Indwelling pleural catheter (IPC): for recurrent effusion, trapped lung, or failed pleurodesis
• VATS decortication: for chronic empyema or trapped lung
• Thoracotomy and decortication: if VATS fails

Referral Criteria

• Undiagnosed exudative effusion after initial aspiration: respiratory referral for thoracoscopy
• Suspected malignant effusion: urgent 2WW cancer pathway
• Empyema not responding to antibiotics/drain: thoracic surgery referral
• Recurrent effusion requiring intervention: IPC or pleurodesis

• Depends entirely on underlying cause
• Heart failure effusion: prognosis related to cardiac disease severity
• Parapneumonic effusion: good prognosis with appropriate antibiotics; empyema mortality ~15-20%
• Malignant effusion: median survival 3-12 months depending on primary tumour
• Lung cancer with malignant effusion: median survival ~4 months
• Breast cancer with malignant effusion: median survival ~12 months
• TB pleuritis: excellent prognosis with treatment (>95% cure)
• Talc pleurodesis success rate: ~70-80%
• IPC achieves spontaneous pleurodesis in ~40-60% over time

Light's Criteria (Exudative Effusion)

Pleural Fluid Appearance

Indications for Chest Drain in Pleural Effusion