Inclusion Criteria:  Infants aged <= 2 years old Medical diagnosis of acute bronchiolitis requiring hospitalization in the pediatric departments of the Besançon University Hospital No opposition from the parents for performing the pleuropulmonary echography.  Exclusion Criteria:  Children aged > 2 years old Infants aged < 2 years old consultant in pediatric emergencies for acute bronchiolitis without subsequent hospitalization. Previous chronic lung disease (including pulmonary bronchodysplasia), unoperated congenital heart disease or neuromuscular disease.