Bronchiectasis (plural: bronchiectases) is defined as an irreversible abnormal dilatation of the bronchial tree. It has a variety of underlying causes, with a common etiology of chronic inflammation. High-resolution CT is the most accurate modality for diagnosis.
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Epidemiology
As there are many causes of bronchiectasis, which may occur at essentially any age, no single demographic is particularly involved. Two groups make up the majority of cases: post-infectious and cystic fibrosis 3.
Clinical presentation
Bronchiectasis typically presents with recurrent chest infections, productive cough more than 8 weeks, production of copious amounts of sputum, and hemoptysis.
Pathology
Etiology
Bronchiectasis is the common response of bronchi to a combination of inflammation and obstruction/impaired clearance. Causes include 1-7,9,17,21:
idiopathic (most common)
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impaired host defenses
cystic fibrosis (most common cause in children)
primary ciliary dyskinesia, e.g. Kartagener syndrome, Young syndrome
primary immunodeficiency disorder, e.g. common variable immunodeficiency, hypogammaglobulinaemia, chronic granulomatous disease
HIV/AIDS 15,16
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postinfective (most common known non-cystic fibrosis cause in adults)
bacterial pneumonia and bronchitis, e.g S. aureus, H. influenzae, B. pertussis
mycobacterial infection, e.g. tuberculosis, Mycobacterium avium-intracellulare complex
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allergic and autoimmune
connective tissue disease, e.g. rheumatoid arthritis 6, Sjögren syndrome, systemic lupus erythematosus (SLE) 7
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obstruction
severe obstructive lung disease: asthma or chronic obstructive pulmonary disease (COPD)
neoplasm, e.g. bronchial carcinoid, bronchogenic carcinoma
inhaled foreign bodies
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congenital
bronchial tree malformations, e.g. Mounier-Kuhn syndrome, Williams-Campbell syndrome, pulmonary sequestration, bronchial atresia
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others
traction bronchiectasis due to diffuse lung disease, e.g. pulmonary fibrosis
post-transplantation
A mnemonic to remember common causes is CAPT Kangaroo has Mounier-Kuhn.
Subtypes
According to macroscopic morphology, three types have been described, which also represent a spectrum of severity 8:
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bronchi have a uniform caliber, do not taper and have parallel walls (tram track sign and signet ring sign)
commonest form 14
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relatively uncommon
beaded appearances where dilated bronchi have interspersed sites of relative narrowing
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severe form with cyst-like bronchi that extend to the pleural surface
air-fluid levels are commonly present
According to one study, the relative prevalence of bronchiectatic changes were 14:
cylindrical: ~ 47%
varicose: ~ 9.9%
cystic: ~ 45.1%
multiple types: ~ 24.3%
Scoring systems
Traction versus non-traction bronchiectasis
Bronchiectasis can result from the traction of fibrotic lung surrounding an airway. This is known as traction bronchiectasis. There is dilation of bronchi and bronchioles due to elastic tissue and smooth muscle destruction.
When not related to regional fibrotic changes then this is described as non-traction bronchiectasis or free-standing bronchiectasis.
Radiographic features
Plain radiograph
Chest x-rays are usually abnormal but are inadequate in the diagnosis or quantification of bronchiectasis. Tram-track opacities are seen in cylindrical bronchiectasis, and air-fluid levels may be seen in cystic bronchiectasis. Overall there appears to be an increase in bronchovascular markings, and bronchi seen end-on may appear as ring shadows 8. Pulmonary vasculature appears ill-defined, thought to represent peri-bronchovascular fibrosis 8,9.
CT
CT and HRCT especially excel at demonstrating the airways and is able to a greater or lesser degree to distinguish some of the various underlying causes.
A number of features are helpful in diagnosing bronchiectasis 8,9:
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bronchus visualized within 1 cm of the pleural surface
especially true of lung adjacent to costal pleura
most helpful sign for early cylindrical change
lack of tapering
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increased bronchoarterial ratio 9
diameter of a bronchus should measure approximately 0.65-1.0 times that of the adjacent pulmonary artery branch
between 1 and 1.5 may be seen in normal individuals, especially those living at high altitude
greater than 1.5 indicates bronchiectasis
A number of ancillary findings are also recognized:
bronchial wall thickening: normally wall of bronchus should be less than half the width of the accompanying pulmonary artery branch
mucoid impaction
Signs described on CT include:
Treatment and prognosis
In general, the treatment of bronchiectasis is medical and involves promoting sputum clearance, using positional physiotherapy, and early and aggressive treatment of pulmonary infections. In some cases, chronic prophylactic administration of antibiotics may be required.
In cases where bronchiectasis is severe and significant morbidity is present, surgical resection of the affected lobe may be of the benefit provided adequate respiratory reserve exists.
In cases where both lungs are extensively involved (e.g. cystic fibrosis) lung transplantation can be considered 10.
History and etymology
The term bronchiectasis is derived from the Greek words bronckos (βρόγχος) meaning airway / loop and ectasis (έκταση) meaning widening.
Differential diagnosis
The differential is in two parts:
causes of a particular distribution of bronchiectasis
mimics of bronchiectasis
Causes of a particular distribution of bronchiectasis
Mimics of bronchiectasis
Conditions that may mimic cystic bronchiectasis include 8:
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