Bronchiectasis


by sanjoea - Date: 2007-04-23 - Word Count: 640 Share This!

Bronchiectasis is a chronic necrotizing infection of the bronchi and bronchioles leading to or associated with abnormal dilation of these airways. It is manifested clinically by cough, fever, and expectoration of copious amounts of foul-smelling, purulent sputum. To be considered bronchiectasis, the dilation should be permanent; reversible bronchial dilation often accompanies viral and bacterial pneumonia. Bronchiectasis has many origins and usually develops in association with the following conditions.

Bronchial obstruction, owing to tumor, foreign bodies, and occasionally mucous impaction, in which the bronchiectasis is localized to the obstructed lung segment, or owing to diffuse obsstructive airway disease, most commonly atopic asthma and chronic bronchitis.

Congenital or heriditary conditions, including congenital bronchiecasis (caused by a defect in the development of bronchi), cystic fibrosis, intalobar sequestration of the lung, immunodeficiency states, and immotile cilia and Kartagener syndromes.

Necrotizing pneumonia, most often caused by the tubercle bacillus or staphylococci or mixed infections.

Etiology and Pathogenesis

Obstruction and infection are the major influences associated with bronchiectasis, and it is likely that both are necessary for the development of full-fledged lesions. After bronchial obstruction, air is resorbed from the airways distal to the obstruction, with resultant atelectasis. Often accompanying atelectasis are early bronchial wall inflammation and the presence of intraluminal secretions that result in dilation of the walls of those airways that are present. These changes are reversible (1) if the obstruction persists, especially during periods of growth because the airways will not be able to develop normally and (2) if there is added infection. Infection plays a role in the pathogenesis of bronchiectasis in two ways: (1) It produces bronchial wall inflammation, with weakening and further dilation and (2) the extensive bronchial and bronchiolar damage causes endobronchial obliteration, with atelectasis, distal to the obliteration and subsequent bronchiectasis around atelectatic areas.

These mechanisms - infection and obstruction are most readily apparent in the severe form of bronchectasis associated with cystic fibrosis. In this disorder, there is squamous metaplasia of the normal respiratory epithelium with impairment of normal mucocilary action infection, necrosis of the bronchial and bronchiolar walls, and subsequent bronchiectasis. In younger children, the changes take the form of bronchiolitis (occlusion of the bronchioles by granulation tissue). But older children tend to develop full-blown bronchiectasis.

In Kartagener syndrome, charaterized by bronchiectasis, sinusitis and sutus inversus, there is a defect in ciliary motility associated with structural abnormalities of cila most commonly absent or irregular dynein arms the structures on the microtubular doublets of cilia that are responsible for the generation of ciliary movement. The lack of ciliary activity interferes with bacterial clearance, predisposes the sinuses and bronchi to infection and affects cell motility during embryogenesis, resulting in the situs inversus. Males with this condition tend to be infertile owing to ineffective mobility of the sperm tail. The syndrome is inherited as an autosomal recessive trait and is variable as about half the patients with defective filia have no situs inversus for uncertain reasons. In some groups of patients , the cilia are not immobile but have abnormal movement (ciliary dyskinesia). More may be involved in the genesis of this syndrome than ciliary abnormalities, since some abnormal cilia may be found in otherwise normal individuals or in patients with viral illnesses and bronchial inflammation.

Clinical Course

Bronchiectasis causes severe persistent cough; expectoration of foul smelling sometimes bloody squtum; and dyspnea and orthopnea in severe cases. A systemic febrile reaction may occur when powerful pathogens are present. These symptoms are often episodic and are precipitated by upper respiraatory tract infections or the introduction of new pathogenic agents. In the full-blown case, the cough is paroxysmal in nature. Such paroxysms are particularly frequent when the patient raises in the morning and the changes in position lead to drainage into the bronchi of the collected pools of pus. Obstructive ventilatory insufficiency can lead to marked dyspnea and cyanosis. Cor pulmonale metastatic brain abscesses, and amyloidosis are less frequent complications of bronchiectasis.

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