Bronchiectasis

Bronchiectasis is a chronic respiratory condition defined by permanent, abnormal dilation of the bronchi, accompanied clinically by persistent cough, daily sputum production, and recurrent respiratory infections. The structurally damaged airways clear secretions poorly, creating a self-sustaining cycle of mucus retention, bacterial colonisation, inflammation, and progressive airway injury.

Definition

Bronchiectasis is a chronic condition characterised by permanent dilation of the bronchi, identified radiologically (typically on high-resolution computed tomography) and expressed clinically as chronic cough, sputum production, and susceptibility to recurrent airway infection, arising from a range of underlying causes.

Scope

This entry covers the definition of bronchiectasis as permanent bronchial dilation, the 'vicious cycle' that perpetuates it, its radiological basis on computed tomography, its many underlying causes, and the concept of exacerbations. It treats bronchiectasis as a clinical and methodological topic and does not provide dosing, individualized diagnosis, or treatment recommendations.

Key concepts

• Permanent bronchial dilation
• Impaired mucociliary clearance
• Vicious cycle (vicious vortex) of infection and inflammation
• Chronic bacterial colonisation
• Acute exacerbations
• High-resolution CT diagnosis
• Heterogeneous underlying aetiologies
• Distinction from cystic-fibrosis bronchiectasis

Mechanisms

The dominant explanatory model is a self-perpetuating cycle in which an initial insult — infection, an underlying immune or structural defect, or impaired airway clearance — leads to retained secretions that promote bacterial colonisation. Persistent infection drives neutrophilic airway inflammation, whose proteolytic and oxidative products damage the bronchial wall, causing the permanent dilation and further impairing clearance, which in turn sustains infection and inflammation. Contemporary accounts describe this as a 'vicious vortex' of interacting elements rather than a single linear loop, and emphasise heterogeneity in the immune, microbial, and genetic factors that initiate and maintain it. Although classed among obstructive airway diseases, bronchiectasis can show obstructive, mixed, or near-normal spirometric patterns depending on the extent and distribution of disease.

Clinical relevance

Once considered uncommon, bronchiectasis is now recognised as an important and not-rare chronic airway disease, and understanding its definition and mechanisms informs how the respiratory literature is appraised. This entry is a reference for what bronchiectasis is and how it is conceptualised; it is descriptive and is not a basis for individual diagnosis or treatment decisions.

Epidemiology

Bronchiectasis is increasingly diagnosed, partly through wider use of computed tomography, and its recognised prevalence rises with age and is higher in women in many series; the term here refers chiefly to bronchiectasis not caused by cystic fibrosis, which is tracked and studied separately. Reported prevalence varies substantially with case definition and population.

History

Bronchiectasis was described by René Laennec in the early nineteenth century in connection with his work on auscultation, and for much of the twentieth century it was regarded as an uncommon disease in resource-rich settings. The advent of high-resolution computed tomography, together with renewed research interest and dedicated management guidelines, restored it as a recognised and actively studied cause of chronic obstructive airway disease.

Debates

How should the disease process best be modelled?

The classical 'vicious cycle' of infection, inflammation, and structural damage has been refined into a 'vicious vortex' framing that treats the contributing elements as mutually reinforcing rather than strictly sequential, with implications for how heterogeneity and treatable traits are conceptualised.

Seminal works

• polverino-2017
• flume-2018

Frequently asked questions

What does it mean that bronchiectasis is 'permanent'?

Unlike the reversible airway narrowing of asthma, the bronchial dilation in bronchiectasis reflects fixed structural damage to the airway walls that does not return to normal, which is why it is defined as permanent dilation.

Is bronchiectasis the same as cystic fibrosis?

No. Cystic fibrosis is a specific genetic disease that commonly causes bronchiectasis, but the term bronchiectasis as used here usually refers to non-cystic-fibrosis bronchiectasis, which has many different underlying causes and is studied as a distinct entity.