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Bronchiolitis, defined as inflammation of the bronchioles, usually is caused by an acute viral infection. Viral bronchiolitis is the most common lower respiratory tract infection in infants and children who are 2 years of age and younger. The most commonly identified infectious agent is the respiratory syncytial virus (RSV). Other identified pathogens include adenovirus, human metapneumovirus, influenza virus, and parainfluenza virus.

The pathophysiology of bronchiolitis begins with an acute infection of the epithelial cells lining the small airways within the lungs. Such infection results in edema, increased mucus production, and eventual necrosis and regeneration of these cells. The clinical presentation of bronchiolitis includes rhinitis, cough, tachypnea, use of accessory respiratory muscles, hypoxia, and variable wheezing and crackles on auscultation.

The evaluation and management of bronchiolitis varies substantially. Although bronchiolitis is a well-recognized clinical syndrome, additional tests such as viral isolation, blood...

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