Bronchiectasis is a disease state defined by localized, irreversible dilation of part of the bronchial tree. It is classified as an obstructive lung disease, along with emphysema, bronchitis and cystic fibrosis. Involved bronchi are dilated, inflamed, and easily collapsible, resulting in airflow obstruction and impaired clearance of secretions. Bronchiectasis is associated with a wide range of disorders, but it usually results from necrotizing bacterial infections, such as infections caused by the Staphylococcus or Klebsiella species or Bordetella pertussis.