Characteristics

• Abnormal permanent enlargement of distal air spaces with destruction of alveolar walls ± lung fibrosis. Overlaps with chronic bronchitis to form a disease spectrum known as chronic obstructive pulmonary disease.

• Due to an imbalance between lung proteases and anti-proteases.

• A bulla is an avascular low attenuation area that is larger than 1 cm and has a thin but perceptible wall.

• Associated with smoking but other chemicals and genetic disorders predispose to the condition (e.g. alpha-1 antitrypsin deficiency).

• Three types of emphysema

1. Panacinar, centrilobular and paraseptal.

• The different types of emphysema may coexist.

Clinical features

• May be asymptomatic, early in the disease.

• Exacerbations commonly precipitated by infection.

• Cough, wheeze and exertional dyspnoea.

• Tachypnoea, wheeze, lip pursing (a form of PEEP), use of accessory muscles (patients are referred to as pink puffers).

• Signs of hypercarbia include coarse tremor, bounding pulse, peripheral vasodilatation, drowsiness, confusion or an obtunded patient.

Radiological features

• CXR – focal area of well-defined lucency outlined with a thin wall. A fluid level may indicate infection within the bulla.

• Other CXR features include hyperexpanded lungs with associated flattening of both hemi-diaphragms, ‘barrel-shaped chest’, coarse irregular lung markings (thickened dilated bronchi – chronic bronchitis overlaps) and enlargement of the central pulmonary arteries in keeping with pulmonary arterial hypertension.

• REMEMBER to look for lung malignancy/nodules; a common association.

• CT quantifies the extent, type and location of emphysema. It may also identify occult malignancy.

Differential diagnosis

• Post-infective pneumatoceles.

• Loculated pneumothorax.

• Oligaemia secondary to pulmonary emboli or hilar vascular compression.

Management

• Emphysematous bullae form part of a spectrum of chronic obstructive pulmonary disease (see p. 62).

• Bullae in their own right usually need no active treatment. However, if severe disease, lung reduction surgery should be considered.