Chest Imaging

Bullae

emphysematous spaces larger than 1 cm. Bullae are generally seen in patients with centrilobular emphysema and/or paraseptal emphysema. The presence of emphysema associated with large bullae is referred to as bullous emphysema. Patients with isolated bullae are usually without signs or symptoms. Occasionally large bullae produce dyspnoea that may necessitate bullectomy. On the chest radiograph, large bullae are seen as avascular transradiant areas usually separated from the remaining lung parenchyma by a thin curvilinear wall of a very variable extent (Fig.1). They can cause marked relaxation collapse of the adjacent lung. They can even extend across into the opposite hemithorax, particularly by way of the anterior junctional area. CT is the best available technique for assessing the number, size and location of bullae, which is essential in cases considered for bullectomy. They are seen as avascular, low attenuation areas that are larger than 1 cm and that can have a thin but perceptible wall (Fig.2).

Bullae may enlarge progressively over months or years; a period of stability may be followed by a sudden expansion. Bullae may also disappear either spontaneously or following infection or haemorrhage. The main complications of bullae include pneumothorax, infection and haemorrhage. In cases of infection or haemorrhage, bullae contain fluid and develop an airfluid level. When bullae become infected the hairline wall become thickened and may mimic a lung abscess.

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Fig.1

PA chest radiograph showing a large bulla in the right upper lobe of an asymptomatic patient.
Bullae, Fig.1
Bullae, Fig.2