What is Giant Bullae?
Giant bullae are sharply demarcated, thin-walled air spaces measuring ≥1 cm in diameter that occupy at least one-third of a hemithorax, typically occurring in the upper lobes and compressing surrounding functional lung parenchyma. 1, 2, 3
Definition and Characteristics
Bullae are defined as focal areas of emphysema that are sharply demarcated by a thin wall and measure 1 cm or more in diameter, distinguishing them from other emphysematous changes that lack distinct walls 1
Giant bullous emphysema (GBE) specifically refers to giant bullae occupying at least one-third of the hemithorax, with the most severe cases potentially occupying an entire hemithorax 3, 4
The condition is also known as vanishing lung syndrome when particularly extensive 5
Clinical Presentation
Symptoms include dyspnea, hypoxia, chest pain and pressure, and hemoptysis, though some patients may remain completely asymptomatic despite massive bullae 3, 6
Patients typically present with progressive shortness of breath, exercise intolerance, and a feeling of chest pressure as the bullae compress adjacent functional lung tissue 6
The condition can be complicated by pneumothorax and infection of the bullae 1, 3
Typical Patient Profile
Giant bullous emphysema typically occurs in young, thin male smokers, though cases have been reported in nonsmoking females 5
- The condition is more common in usual (non-alpha-1 antitrypsin deficiency) emphysema compared to AAT deficiency-related emphysema 1
Radiographic Appearance
On chest radiography, bullae appear as areas of increased radiolucency with visible thin walls, though early disease may show normal chest X-rays 1
High-resolution CT (HRCT) is much more sensitive than plain chest radiography for detecting bullous disease, showing areas of abnormally low attenuation (–600 to –800 Hounsfield units) with sharply demarcated thin walls 1
In advanced cases, bullae demonstrate hyperinflation, low and flat diaphragms, and decreased vascular markings 1
Critical Diagnostic Pitfall
Giant bullous emphysema can be mistaken for traumatic pneumothorax, particularly in emergency settings where patients present with respiratory distress and absent breath sounds 3
A CT scan plays an essential role in differentiating GBE from pneumothorax, as needle decompression or chest tube insertion into a giant bulla can be catastrophic, causing high-flow air fistulas and potentially fatal complications 3
If the patient is clinically stable and pneumothorax is suspected, imaging studies should be performed prior to chest tube placement to avoid this potentially lethal error 3
Associated Conditions
Giant bullae may be found in association with emphysema and represent pockets of entrapped air that grow as surrounding lung retracts away 6
In late stages, fibrosis and apical blebs/bullae and cysts may develop 1
Bullae do not participate in gas exchange and merely occupy space, leading to severe impediment of mechanical ventilation in adjacent lung parenchyma 6
Risk During Air Travel
Patients with large bullae face theoretical risk of pneumothorax during air travel, as bullae can expand by 30% at typical cruising altitude due to reduced cabin pressure 2
- A history of pneumothorax or presence of emphysematous bullae represents a relative contraindication to air travel 2