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Classification The Reid classification of bronchiectasis is based on anatomic and morphologic patterns of airway dilation. In cylindrical bronchiectasis, bronchi are uniformly dilated and thick walled and extend to the lung periphery without normal tapering. The number of bronchiolar subdivisions is normal; however, on bronchograms, the number is artifactually small because of secretions plugging smaller bronchi and bronchioles. In varicose bronchiectasis, local constrictions cause an irregular or beaded bronchial outline, with alternating areas of constriction and dilation, similar to saphenous varicosities. Examination on microscopic section reveals that the number of bronchial subdivisions is reduced by half. Cystic bronchiectasis is the most severe form of the disease and is commonly found in patients with cystic fibrosis. In cystic bronchiectasis, the bronchi are dilated, forming a cluster of round air- or fluid-filled cysts. Patients with cystic bronchiectasis have only 25% of the normal number of bronchial subdivisions.
These three forms of bronchiectasis—cylindrical, varicose, and cystic—can all exist in one patient. Another form of bronchiectasis, follicular, is defined histologically. Follicular bronchiectasis is characterized by excessive lymphoid nodules and follicles within thickened bronchial walls. The bronchioles are lined with hyperplastic, mucus-secreting glands that are usually devoid of cilia. Follicular bronchiectasis usually occurs after pneumonia in children with measles, pertussis, or adenovirus infections.
Pathophysiology Bronchiectasis is thought to result from accumulation of infected secretions and chronic inflammation within the airway that progresses to destruction of the bronchial tree and surrounding lung parenchyma. Bronchiectasis begins with an initial insult that damages the bronchial epithelium and decreases mucociliary clearance. Pathogens such as Haemophilus influenzae, Staphylococcus aureus, and Pseudomonas aeruginosa colonize the stagnant mucus and cause infection. The infection stimulates an inflammatory response, with neutrophils migrating to the affected area. Neutrophils release proteolytic enzymes, such as neutrophil elastase, that damage bronchial epithelial cells and cilia, overwhelming protective proteases in the lung. Studies have shown that patients with bronchiectasis have increased levels of neutrophil elastase in their sputum. When supernatant from the bronchiolitic sputum was added to cultured bovine tracheal cells, secretory activity increased. This secretory activity was attenuated (70%) by a selective human neutrophil elastase inhibitor, suggesting that neutrophil protease inhibitors play a role in reducing mucous hypersecretion. Patients with bronchiectasis also have high concentrations of interleukin (IL)-8 in their sputum. A monoclonal antibody to IL-8 significantly inhibited (75% to 98%) neutrophil chemotaxis, suggesting that blockade of neutrophil chemotaxis mediators may attenuate inflammation by curtailing neutrophil recruitment and release of proteolytic enzymes. Studies in symptomatic, stable patients with bronchiectasis revealed that these patients have chronic, ongoing inflammation with systemic effects. Markers of systemic inflammation-increased serum globulin level, increased peripheral leukocyte count, decreased serum albumin level-were significantly associated with the degree of lung impairment. These markers may help predict progressive lung deterioration in patients with bronchiectasis. A number of underlying conditions predispose patients to the development of bronchiectasis (Table 9). Of all underlying conditions, cystic fibrosis is now the most common. Other predisposing factors include a history of childhood or adult pulmonary infections (viral, bacterial, or mycobacterial), obstruction, congenital anatomic defects, immunodeficiency states, hereditary abnormalities, a 1-antitrypsin (AAT) deficiency, inflammatory bowel disease, and Young’s syndrome.
TABLE 9 Predisposing Conditions for Bronchiectasis
Clinical Findings For most patients, symptoms of bronchiectasis develop in childhood. Symptomatic patients with bronchiectasis often present with recurrent respiratory infection, chronic cough, and persistent production of large quantities of purulent and often foul-smelling sputum. Systemic manifestations of persistent infection-specifically, fever, weight loss, and digital clubbing may also be present. Other symptoms of bronchiectasis include anaemia, bronchovesicular sounds, sinusitis, and hemoptysis. Hemoptysis occurs more commonly in patients with "dry bronchiectasis," that is, bronchiectasis not associated with sputum production.
Anatomic distribution of bronchiectasis often involves middle and left lower lobes and lingula. Bronchiectasis caused by cystic fibrosis, allergic bronchopulmonary aspergillosis (ABPA), tuberculosis, or chronic fungal infection often involves the upper lobe. With the exception of bronchiectasis caused by ABPA, most cases involve distal bronchial segments. Until recently, bronchography was the most accurate diagnostic procedure for evaluating bronchiectasis. High-resolution computed tomography (HRCT) is now preferred to bronchography for diagnosing bronchiectasis in most patients because it is non-invasive, avoids allergic reactions to contrast media, and is more sensitive and specific. Bronchography is still recommended for select surgical candidates in whom HRCT has documented segmental or unilateral involvement. The three forms of bronchiectasis as defined by the Reid classification can be diagnosed using HRCT. Cylindrical bronchiectasis is confirmed by the presence of parallel "tram track" lines (horizontal orientation) or a "signet ring" appearance (cross-sectional orientation, dilated bronchus with the pulmonary artery representing the stone). Varicose bronchiectasis is identified by an irregular or beaded outline of the bronchi, with alternating areas of constriction and dilation. Cystic bronchiectasis is identified through its characteristic, large cystic spaces or "honey combing" appearance. Bronchoscopy, although not a useful diagnostic tool, is used to help identify underlying abnormalities in proximal airways, such as foreign bodies, tumors, and obstructing lesions associated with the development of bronchiectasis. Bronchoscopy is also used to obtain specimens for culture when directing antibiotic therapy. Table 10 includes recommendations for the diagnostic evaluation of bronchiectasis in patients with recurrent respiratory infection and persistent production of purulent sputum. TABLE 10 Diagnostic Evaluation of Bronchiectasis in Recurrent Respiratory Infectionsum
Treatment The goal of therapy for patients with bronchiectasis is to relieve symptoms, prevent complications, control exacerbations, and reduce morbidity and mortality. Successful management depends on the early recognition of bronchiectasis and any underlying disorders. Generally, medical management of bronchiectasis includes antibiotic therapy and chest physical therapy with postural drainage and chest clapping. Patients with exacerbations of bronchiectasis are commonly hospitalized and treated with intravenous antibiotics and bronchodilators, aggressive physiotherapy, and supplemental nutrition. Smoking cessation, avoidance of tobacco smoke, and immunizations for influenza and pneumococcal bacteria are recommended for patients with bronchiectasis.Oral, parenteral, and aerosolized antibiotics are used to decrease bacterial load and control exacerbations. However, continuous antibiotic prophylaxis is not generally indicated for patients because of the emergence of resistant organisms. Postural drainage with percussion and vibration is used to mobilize and promote mucus clearance; the benefits of these techniques, however, have not been consistent. Some success has been obtained with other techniques used to enhance drainage, such as vigorous cough and exercise. Concomitant use of nebulized bronchodilators and chest physiotherapy has been shown to increase secretion clearance in patients with bronchiectasis. The clinical benefit of corticosteroid therapy in the treatment of patients with bronchiectasis has yet to be determined. In a study of patients with bronchiectasis secondary to cystic fibrosis, inhaled beclomethasone dipropionate had no beneficial treatment effect. On the other hand, in a study evaluating the effects of oral prednisone in patients with cystic fibrosis, treatment over 4 years decreased the number of hospitalizations and improved pulmonary function. Other treatments for bronchiectasis include dietary supplements to enhance nutritional status and oxygen therapy to treat hypoxemia and progressive respiratory failure. Surgery is sometimes an important adjunct to therapy in select patients with advanced disease (for example, patients who require frequent hospitalization, patients whose disease progresses despite medical management, and patients with localized disease). Infections caused by foreign bodies are treated by removal of the foreign material and administration of antibiotics. Inhaled bronchodilators are used to reduce bronchial hyper responsiveness in some patients. Intravenous immunoglobulins are effective in treating patients with immunodeficiency due to hypogammaglobulinemia. Intravenous AAT can be used to restore anti-elastase activity. Aerosolized recombinant DNase has had no beneficial treatment effects in patients with bronchiectasis (not caused by cystic fibrosis); however, recombinant DNase is approved for the treatment of patients with cystic fibrosis and has been shown to improve FEV1, reduce use of parenteral antibiotics, and improve dyspnea and quality of life in that population.
Complications Primary complications of bronchiectasis include recurrent pulmonary infections that require hospitalization and treatment with parenteral antibiotics, focal lung abscesses, hemoptysis, chronic respiratory insufficiency, and corpulmonale. Recurrent pulmonary infection is the most common cause of morbidity in patients with bronchiectasis. Progressive respiratory insufficiency and corpulmonale are the most common causes of pulmonary-related death. For patients with cystic fibrosis, the prevalence of hemoptysis ranges from 10% to 62%. Treatment for severe hemoptysis is bronchial artery embolization or surgery. |
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