|
Bronchiectasis
is dilation and destruction of larger bronchi caused by chronic
infection and inflammation. Common causes are cystic fibrosis, immune
defects, and recurrent infections, though some cases appear to be
idiopathic. Symptoms are chronic cough and purulent sputum expectoration;
some patients may also have fever and dyspnea. Diagnosis is based
on history and imaging, usually involving high-resolution CT, though
standard chest x-rays may be diagnostic. Treatment and prevention
of acute exacerbations are with antibiotics, drainage of secretions,
and management of complications, such as superinfection and hemoptysis. Treatment
of underlying disorders is important whenever possible.
Etiology
Bronchiectasis may affect many areas of the lung (diffuse bronchiectasis), or it may appear in only one or two areas (focal bronchiectasis). Diffuse bronchiectasis develops in patients with genetic, immune, or anatomic defects that affect the airways. Cystic fibrosis is the most common cause. Immunodeficiencies may also cause diffuse disease, as may rare abnormalities in airway structure. Diffuse bronchiectasis is an uncommon complication of more common conditions, such as RA or Sjögren's syndrome. Allergic bronchopulmonary aspergillosis is a hypersensitivity reaction to Aspergillus sp (see Asthma: Allergic Bronchopulmonary Aspergillosis (ABPA)). It occurs primarily in people with asthma and less commonly in people with cystic fibrosis and can lead to bronchiectasis.
Focal bronchiectasis develops from untreated pneumonia or obstruction (eg, from foreign bodies and tumors). Mycobacteria can cause focal bronchiectasis as well as colonize the lungs of patients with bronchiectasis due to other disorders (see
Table 1: Bronchiectasis: Factors Predisposing to Bronchiectasis ). Some cases have no readily apparent cause.
Pathophysiology
All the causative conditions impair airway clearance mechanisms and host defenses, resulting in an inability to clear secretions, which, in turn, predisposes patients to chronic infection and inflammation. As a result of frequent infections, most commonly with Haemophilus influenzae (35%), Pseudomonas
aeruginosa (31%), Moraxella catarrhalis (20%), Staphylococcus
aureus (14%), and Streptococcus pneumoniae (13%), airways become inspissated with viscous mucous containing inflammatory mediators and pathogens and slowly become dilated, scarred, and distorted. Histologically, bronchial walls are thickened by edema, inflammation, and neovascularization. Destruction of surrounding interstitium and alveoli causes fibrosis, emphysema, or both.
Superinfection with multidrug-resistant organisms, including Mycobacterium tuberculosis, and mycobacteria other than M. tuberculosis can cause recurrent exacerbations and worsen airflow limitation on pulmonary function tests. Pulmonary hypertension and right-sided heart failure may ensue because functional lung tissue decreases.
Symptoms and Signs
Symptoms characteristically begin insidiously and gradually worsen over years. The major presenting symptom of bronchiectasis is chronic cough that almost always produces large volumes of thick, tenacious, purulent sputum. Dyspnea and wheezing are common. Hemoptysis, which can be massive, is due to neovascularization of the airways from the bronchial (as opposed to pulmonary) arteries. Acute exacerbations of disease from new or worsened infection increase the extent of cough and the volume and purulence of sputum production. Low-grade fever may also be present.
Halitosis and abnormal breath sounds, including crackles, rhonchi, and wheezing, are typical signs of disease. Finger clubbing may also be present. In advanced cases, hypoxemia and signs of pulmonary hypertension (eg, shortness of breath, dizziness) and right-sided heart failure can occur.
Diagnosis
Diagnosis is based on a history, physical examination, and radiologic testing, beginning with a chest x-ray. Chronic bronchitis may mimic bronchiectasis clinically, but bronchiectasis is distinguished by more voluminous daily production of purulent sputum and by dilated airways on imaging studies.
Imaging:
X-ray findings suggestive of bronchiectasis include scattered irregular opacities caused by mucous plugs, honeycombing, and rings and “tram lines” caused by thickened, dilated airways located perpendicular to the x-ray beam. Radiographic patterns may differ by underlying disease: Bronchiectasis due to cystic fibrosis develops predominantly in upper lobes, whereas that due to other causes is more diffuse or predominates in the lower lobes.
High-resolution CT is the test of choice for defining the extent of bronchiectasis. The test is nearly 100% sensitive and specific. CT typically shows thickening of airways characterized by tram-track parallel lines or ring shadows representing thickened bronchial walls when imaged in cross-section. Cysts (sometimes appearing as grapelike clusters), scattered mucous plugs, and airways that are dilated > 1.5 times the diameter of nearby blood vessels can also be seen. Dilated medium-sized bronchi may extend almost to the pleurae. Atelectasis, consolidation, and decreased vascularity are nonspecific findings. A differential diagnosis of dilated airways includes bronchitis and traction bronchiectasis that occurs when pulmonary fibrosis pulls airways open.
Pulmonary function
tests:
Pulmonary function tests can be helpful for documenting baseline function and for following the progression of disease over time. Bronchiectasis causes airflow limitation (reduced forced expiratory volume in 1 sec [FEV1], forced vital capacity [FVC], and FEV1/FVC); the FEV1 can improve in response to β-agonist bronchodilators. Lung volume measurements may be increased or decreased and diffusing capacity for carbon monoxide (DLco) may be decreased.
Diagnosis of
cause:
Tests to help diagnose a cause include sputum evaluation, including staining and cultures for bacterial, mycobacterial (M.
avium complex and M.
tuberculosis), and fungal (Aspergillus) infection. Mycobacterial superinfection is diagnosed by repeatedly culturing mycobacteria other than TB in high colony counts and by finding granulomas on biopsy with concurrent radiologic evidence of disease. Additional tests may include the following:
When the clinical presentation suggests ciliary dyskinesia (by concurrent sinus disease and middle and lower lobe bronchiectasis with or without infertility), a nasal or bronchial epithelial sample should be obtained and examined by transmission electron microscopy for abnormal ciliary structure. A less invasive alternative is examination of sperm motility. The diagnosis of ciliary dyskinesia should be made cautiously by an experienced physician trained in specialized electron microscopic techniques because nonspecific structural defects can be present in up to 10% of cilia in healthy patients and in patients with pulmonary disease; infection can cause transient dyskinesia; and ciliary ultrastructure may be normal in patients with primary ciliary dyskinesia syndromes characterized by abnormal ciliary function.
Bronchoscopy is indicated when an anatomic or an obstructing object or lesion is suspected.
Prognosis
Overall, prognosis is thought to be good, with about 80% of patients having no further deterioration of lung function on the basis of bronchiectasis alone. However, cystic fibrosis patients have a median survival of 36 yr, and most patients continue to have intermittent acute exacerbations.
Treatment
There is no consensus on the best approach to prevent or limit acute exacerbations. Options include daily prophylactic oral antibiotics (eg, ciprofloxacin 500 mg bid) and, in patients who have cystic fibrosis and are colonized with P. aeruginosa
, inhaled tobramycin (300 mg bid every other month). In patients with diffuse bronchiectasis due to other causes, aerosolized gentamicin (40 mg bid) may also be effective. Chronic therapy with azithromycin 500 mg po 3 times/wk has demonstrated efficacy in patients with cystic fibrosis; it is unclear whether macrolides are useful in other patients. The mechanism of this effect is not known and may not be due to antibiotic effect.
As with all patients with chronic pulmonary disease, annual vaccination against influenza and vaccination every 5 yr against pneumococcus is recommended.
Various techniques can facilitate clearance of secretions, including postural drainage and chest percussion, positive expiratory pressure devices, intrapulmonary percussive ventilators, pneumatic vests, and autogenic drainage (a breathing technique thought to help move secretions from peripheral to central airways). Nebulized drugs, including a mucolytic (rhDNase) or hypertonic (7%) saline, have clinical utility in patients with cystic fibrosis. Patients should be introduced to these techniques by a respiratory therapist and should use whichever technique is most effective for them as no evidence favors one technique.
Additional treatment depends on the cause. For cystic fibrosis, see Cystic Fibrosis (CF). Allergic bronchopulmonary aspergillosis is treated with corticosteroids and possibly with azole antifungals (see Asthma: Allergic Bronchopulmonary Aspergillosis (ABPA)). Patients with immunoglobulin or α1-antitrypsin deficiencies should receive replacement therapy.
Acute exacerbations:
Acute exacerbations are treated with antibiotics and increased efforts to clear sputum from the airways with the use of bronchodilators and mucolytics. Inflammation may be treated with inhaled or oral corticosteroids. Antibiotic choice depends on whether patients have cystic fibrosis or non–cystic fibrosis bronchiectasis.
Antibiotics for non–cystic fibrosis bronchiectasis should initially cover H.
influenzae, P. aeruginosa, M.
catarrhalis, S. aureus, and S.
pneumoniae (eg, ciprofloxacin 500 mg po bid or levofloxacin 500 mg po once/day for 7 to 14 days) and should be adjusted according to culture results.
Antibiotic selection for cystic fibrosis exacerbations is guided by sputum culture. Routine annual sputum cultures should be done on all patients with cystic fibrosis. During childhood, common infecting organisms are S.
aureus and H. influenzae and quinolone antibiotics such as ciprofloxacin and levofloxacin may be used. In the later stages of cystic fibrosis, infections involve highly resistant strains of certain gram-negative organisms including P.
aeruginosa, Burkholderia cepacia, and Stenotrophomonas maltophilia. In these patients, treatment is with multiple antibiotics (eg, tobramycin , aztreonam , ticarcillin -clavulanate, ceftazidime , cefepime ). IV administration is frequently required.
Complications:
Significant hemoptysis is usually treated with bronchial artery embolization, but surgical resection may be considered if pulmonary function is adequate.
Superinfection with mycobacterial organisms such as M. avium complex almost always requires multiple drug regimens that include clarithromycin 500 mg po bid or azithromycin 250 mg once/day; rifampin 600 mg po once/day or rifabutin 300 mg po once/day; and ethambutol 25 mg/kg po once/day for 2 mo followed by 15 mg/kg once/day. Drug therapy is modified based on culture and sensitivity results. All drugs should be taken until sputum cultures have been negative for 12 mo.
Surgical resection for localized bronchiectasis is rarely needed but is considered when medical therapy has been optimized and the symptoms are intolerable. In certain patients with diffuse bronchiectasis, lung transplantation is also an option. Five-year survival rates as high as 65 to 75% have been reported when a heart-lung or double lung transplantation is used. Pulmonary function usually improves within 6 mo, and the improvement may be sustained for at least 5 yr.
Last full review/revision February 2008 by Joshua O. Benditt, MD
Content last modified February 2008
| 
