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Introduction

Bronchiectasis (broncos, airways; ectasia, dilatation) is a morphologic term used to describe abnormal, irreversibly dilated and thick-walled bronchi. This is an anatomic definition that evolved from Laennec’s original description in 1819 of ectatic bronchi in pathologic specimens. Bronchiectasis represents the end stage of a variety of pathologic processes that cause destruction of the bronchial wall and its surrounding supporting tissues. Etiologies include prior lung infection, systemic inflammatory disorders, and genetic disorders of host defense, however, bronchiectasis is considered to be idiopathic in up to half of the affected individuals. The clinical manifestations include chronic cough and copious mucopurulent expectoration.1 Bronchiectasis shares many features with chronic bronchitis, including inflamed and easily collapsible airways, airflow obstruction on spirometry, and frequent exacerbations.

Prevalence

Bronchiectasis was a common disabling and fatal condition in the pre-antibiotic era and remains more common in medically underserved regions of the world. Overall, it is an important cause of suppurative lung disease with a significant impact on the quality of life of affected individuals and on the health system as patients utilize many medical care resources including frequent clinic visits, hospitalizations, diagnostic imaging such as high-resolution computed tomography scan (HRCT) of the chest and parenteral antibiotics.2 In the United States, the overall prevalence has been estimated to be 52 per 100,000, but varies by age. In persons aged 18 to 34 years the prevalence is approximately 4.2 per 100,000 but in those who are 75 years old or it is estimated to be greater than 272 per 100,000. There are an estimated 110,000 affected individuals in the United States.3 In most series, 60% of affected individuals are women. The incidence is higher in some ethnic groups living in isolated regions including the native peoples in Alaska, Maori populations in New Zealand and the Pacific, and Aboriginal groups in Central Australia. In North America and Europe, improved health care has decreased the incidence, thus bronchiectasis due to cystic fibrosis (CF) and other genetic diseases now significantly contribute to the fraction of affected adults.

Pathophysiology

The pathogenesis of bronchiectasis is not known in many cases, and in others may vary with etiology, so that the pathophysiology often remains descriptive. Gross pathology reflects chronic changes so that initial changes of injury proposed to lead to initial airway obstruction are not often observed. The abnormal bronchial dilatation in bronchiectasis principally affects the medium-sized bronchi, but typically extends to the distal bronchi and bronchioles. On gross examination of surgically resected or autopsied lungs, the affected bronchi and bronchioles are so prominent as to be visible all the way to the pleural surface. These dilated and ectatic bronchi are commonly filled with purulent secretions. The affected bronchi show transmural inflammation, mucosal edema, cratering, ulceration, and neovascularization. The bronchial epithelium may show a polypoidal appearance due to underlying granuloma formation and lymphoid aggregates, ridging due to bronchial smooth muscle ...

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