also associated with worse outcomes and more severe disease in bronchiectasis. The initial lung injury in bronchiectasis leads to an impaired mucociliary clearance of the lung airways, which leads to mucous stasis. This mucous stasis leads to bacterial colonization in bronchiectasis which leads to neutrophil activation. This neutrophil activation leads to further further tissue destruction and airway distortion by neutrophils in addition to direct tissue destruction by the pathogenic bacteria. The distorted, damaged lung airways thus have impaired mucociliary clearance; leading to mucous stasis and bacterial colonization leading to further neutrophil activation and thus fueling a self-perpetuating "vicious cycle" of inflammation in bronchiectasis. This "vicious cycle" theory is the generally accepted explanation for the pathogenesis of bronchiectasis. Endobronchial tuberculosis commonly leads to bronchiectasis, either from bronchial stenosis or secondary traction from fibrosis. Traction bronchiectasis characteristically affects peripheral bronchi (which lack cartilage support) in areas of end-stage fibrosis. Diagnosis The goals of a diagnostic evaluation for bronchiectasis are radiographic confirmation of the diagnosis, identification of potential treatable causes, and functional assessment of the patient. A comprehensive evaluation consists of radiographic imaging, laboratory testing, and lung function testing. Laboratory tests that are commonly part of the initial evaluation include a complete blood count, sputum cultures for bacteria, mycobacteria, and fungi, testing for cystic fibrosis, and immunoglobulin levels. Additional tests that are sometimes indicated include testing for specific genetic disorders. Lung function testing is used for the assessment and monitoring of functional impairment due to bronchiectasis. These tests may include spirometry and walking tests. Obstructive lung impairment is the most common finding but restrictive lung impairment can be seen in advanced disease. Flexible bronchoscopy may be performed when sputum studies are negative and a focal obstructing lesion is suspected. A chest x-ray is abnormal in most patients with bronchiectasis. Computed tomography is recommended to confirm the diagnosis and is also used to describe the distribution and grade the severity of the disease. Radiographic findings include airway dilation, bronchial wall thickening, and atelectasis. There are three types bronchiectasis that can be seen on CT scan, namely cylindrical, varicose, and cystic bronchiectasis. Prevention In preventing bronchiectasis, it is necessary to prevent the lung infections and lung damage that can cause it. Children should be immunized against measles, pertussis, pneumonia, and other acute respiratory infections of childhood. Additionally, parents should stay alert to keep children from inhaling objects such as pieces of food or small toys