Pleural effusion, empyema and pneumothorax in children

Overview

The pleural space normally holds only a thin film of fluid. In children it fills most often with pus after pneumonia (empyema); other fluid, blood or air can also collect. Each presses on the lung, reduces ventilation and, if large, pushes the mediastinum across. PGET questions usually test fluid analysis, physical signs and when to drain.

Pleural effusion

Definition and types

• Pleural effusion: excess fluid in the pleural space.
• Transudate: clear fluid from an imbalance of hydrostatic and oncotic pressure; often bilateral.
• Exudate: protein-rich fluid from inflamed pleura with leaky capillaries.
• Empyema: pus in the pleural space.
• Also: haemothorax (blood), chylothorax (lymph).

Causes

Respiratory pathophysiology

• Fluid compresses the lung beneath it, causing pain, breathlessness and, if large, respiratory insufficiency.
• A large collection (Nelson: more than half the hemithorax) pushes the mediastinum to the opposite side and compromises breathing, particularly in young children.
• Inflamed pleura causes pleuritic pain, so the child splints the chest.

Clinical features

• Features of the cause: fever and toxicity in pneumonia or empyema; oedema in nephrotic syndrome; heart failure signs.
• Pleuritic chest pain, breathlessness, respiratory distress if large.
• Reduced chest movement on the affected side.
• Trachea and mediastinum displaced to the opposite side.
• Stony dull percussion.
• Reduced or absent breath sounds and reduced vocal resonance and fremitus.

Pleural fluid analysis

Radiological diagnosis

• Chest X-ray: small effusion blunts the costophrenic angle; larger ones form a homogeneous opacity that hides the lung; very large ones shift the mediastinum away. Nelson adds a decubitus view to show fluid layering.
• Ultrasound: confirms and localises fluid, sizes it and detects loculations.
• CT separates pleural fluid from lung or pleural masses and also shows loculations (Nelson).

Medical and procedural management

• Treat the cause (pneumonia, TB, nephrotic syndrome, heart failure).
• Small effusions, especially transudates: usually no drainage needed.
• Diagnostic tap (thoracocentesis): microscopy, Gram and ZN stains, culture, biochemistry.
• Large effusion or pus (empyema): drain with a chest tube.
• Empyema: IV antibiotics for 2 to 4 weeks guided by culture.
• Thick, loculated parapneumonic effusion or empyema (Nelson): a chest tube alone is often not enough; drainage is best achieved with fibrinolytic agents instilled through the chest tube or video-assisted thoracoscopic surgery (VATS). Both cut morbidity and hospital stay. Many small to moderate parapneumonic effusions settle with IV antibiotics alone.
• TB effusion: anti-tuberculous treatment.
• Pleural biopsy if the diagnosis is still unclear after the tap.

Prognosis is excellent when the cause is treated successfully.

Pneumothorax

Definition

Air in the pleural space, usually leaking from the lung.

Causes

• Secondary to lung disease: pneumonia (usually with empyema), lung abscess, gangrene, infarct, asthma (burst bleb), cystic fibrosis, foreign body.
• Trauma and procedures.
• Primary spontaneous pneumothorax (no underlying cause) occurs in teenagers, more often in tall, thin males and smokers (Nelson).
• Spontaneous pneumothorax has two chief causes (Akbar):
  • rupture of a subpleural bulla or bleb (or the lung end of a pleural adhesion);
  • rupture of a subpleural tuberculous focus into the pleura.

Classification and pathophysiology

Clinical features

• Ranges from no symptoms to severe distress; onset usually sudden.
• Pain or tightness on the affected side, worse on deep breathing; breathlessness; cyanosis if large.
• Signs of a large pneumothorax: reduced chest movement, hyperresonance, reduced or absent breath sounds on the affected side, trachea deviated to the opposite side.
• A small, localised pneumothorax may have no signs.
• Hydropneumothorax: a sharp level, with tympany above and dullness below.
• Tension: worsening distress, hypotension, narrow pulse pressure, falling cardiac output.

Effusion versus pneumothorax

Chest X-ray findings

• Air in the pleural space, outlining the edge of the lung.
• Large or tension: collapse of the underlying lung and mediastinal shift to the opposite side.
• Shows any fluid level (hydro- or pyopneumothorax) and the underlying lung disease.
• Differential on X-ray: congenital diaphragmatic hernia, lung cysts, congenital lobar emphysema, cystic adenomatoid malformation.

Definitive management

• Small or symptom-light pneumothorax in an otherwise healthy child: observe closely; it usually resolves in about 1 week (Akbar). Nelson defines small as under 20% of the hemithorax.
• Breathing 100% oxygen speeds absorption by washing nitrogen out of the blood.
• Larger or symptomatic pneumothorax: needle aspiration, followed by a chest tube (closed thoracostomy).
• Tension pneumothorax: immediate drainage, preferably by chest tube; in an emergency a simple needle aspiration may suffice until a tube is placed (Nelson).
• Analgesia for pleural pain; treat the underlying lung disease.
• Recurrent spontaneous pneumothorax (common in older children): pleurodesis, chemical (talc or doxycycline through the tube) or by surgical abrasion; VATS or thoracotomy allows blebs to be resected (Nelson).

Complications and ICU or referral indicators

• Tension with compromised cardiac function (hypotension, narrow pulse pressure).
• Persistent air leak (bronchopleural fistula): the lung cannot re-expand.
• Hydropneumothorax or pyopneumothorax with pneumonia and empyema.
• Recurrence, especially in older children.

In words, a child needs urgent senior or intensive care input when there is tension or circulatory compromise, a rising oxygen requirement, a leak that does not seal, or serious underlying lung disease such as cystic fibrosis.

Quick revision

• Effusion: transudate (pressure) or exudate (inflammation); empyema = pus.
• Children: empyema commonest; pneumococcus, Hib, S. aureus, TB.
• Exudate: protein ratio over 0.5, LDH ratio over 0.6, glucose under 40, pH under 7.10 in empyema.
• TB effusion: lymphocytes; bacterial: neutrophils.
• Signs: stony dull, reduced breath sounds and vocal resonance, mediastinum pushed away.
• X-ray: blunt angle to homogeneous opacity; ultrasound shows loculations.
• Empyema: chest tube plus IV antibiotics 2 to 4 weeks.
• Pneumothorax: hyperresonant, absent breath sounds, trachea away.
• Types: closed, open (bronchopleural fistula), tension (one-way valve).
• Small: observe (about a week); large: aspirate then chest tube; tension: decompress at once.

Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).

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