Bronchiectasis

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What is Bronchiectasis?

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Bronchiectasis is a disease of the lung.

The lung is composed of large airways (bronchi), which progressively divide and become smaller airways (bronchioles), which eventually terminate as 'alveoli' - the small folded membranes, shaped like a bunch of grapes where gas exchange takes place. (Learn more about the The Respiratory System.)

The small and medium airways are normally free of mucus. Any mucus present is sweeped up by the cilia to the upper airways, and the person then coughs it up.

Bronchiectasis is a chronic infection of the lung airways leading to abnormal and permanent dilatation of the medium and smaller airways (bronchi and bronchioles). This allows mucous to accumulate and remain stagnant, and subsequently become infected leading to repeated lung infections.

Who gets Bronchiectasis?

In Australia the prevalence of this condition is 1.5% among children aged 15 and under. It has also been found recently that approximately 29 - 50% of patients with chronic obstructive pulmonary disease (COPD) have associated bronchiectasis.

Predisposing Factors

Bronchiectasis can be congenital (the person is born with a predisposition to the disorder), or acquired (develops as a result of another process):

Congenital defects:

Cystic fibrosis is an important cause of Bronchiectasis. There is increased viscid mucous secretion which remains stagnant, and is later infected.
Primary ciliary dyskinesia is a disorder in which the lung's cilia are not functioning properly. The cilia are little 'hairs' on the inside of a bronchus which sweep mucous up towards the trachea. In this disorder the cilia are 'immotile' i.e. not moving, thus allowing mucous to accumulate in the lower airways and get infected.

Acquired:

Bronchiectasis may be initiated by certain infections, e.g. adenovirus, M. pneumoniae, measles, pneumonia, whooping cough, or tuberculosis .
Exposure to chemical irritants (e.g. aspiration pneumonia, ammonia inhalation) can lead to airway inflammation and bronchiectasis.
Disorders of immunological deficiency (HIV, hypogammaglobulinemia) or over-response (allergic bronchopulmonary aspergillosis) are associated with the disease.
Chronic mechanical obstruction of a bronchus by a tumour or foreign body can also predispose a patient to bronchiectasis.
Lung fibrosis (e.g. connective tissue disease, idiopathic pulmonary fibrosis) can increase the tension on the bronchi, leading to airway dilatation and "traction bronchiectasis".

In all of the above disorders, the ultimate end result is dilation of the smaller bronchi and bronchioles. Mucous remains stagnant in the smaller airways and subsequently gets infected, which leads to more damage to the wall of the bronchus, thus making it weaker and more dilated, initiating a vicious cycle.

Progression

Symptoms have often been present for a number of years and are often initiated by an episode of pneumonia. The bronchial walls become inflamed, thickened and permanently damaged. More mucous accumulates in the dilated airways, predisposing the lungs to further bacterial infections. Persistent mucous production and airway obstruction leads to lung collapse and a reduction in the elastic forces holding the airways taught.

Common complications include: pneumonia, haemoptysis - coughing up blood (may be severe and life-threatening), abscesses travelling to other parts of the body (eg brain), respiratory failure, and right heart failure..

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