Which finding on physical examination is specific to bronchiolitis?

Rales, also known as crackles, are a finding that is specifically associated with bronchiolitis. This condition is characterized by inflammation and obstruction of the small airways (bronchioles) in the lungs, often due to viral infections such as respiratory syncytial virus (RSV). During physical examination, the presence of rales indicates the movement of air through fluid or secretions in the airways, which is a hallmark sign of bronchiolitis resulting from the narrowing or blockage of these small airways.

In contrast, other findings might not be unique to bronchiolitis. Fremitus can be affected by various factors and conditions including lung consolidation, making it less specific. Clubbing generally indicates chronic pulmonary conditions or other systemic issues, rather than acute viral infections like bronchiolitis. Decreased breath sounds can result from many different pulmonary issues, such as pleural effusions or significant airway obstruction, thus lacking specificity to bronchiolitis.

Therefore, the presence of rales is a key indicator of the pathological changes occurring in bronchiolitis, making it the specific finding in this context.