Bronchiolitis is the leading cause of hospitalization in infants. The diagnosis is clinical and chest x-ray (CXR) should be reserved for severe cases in which signs of pulmonary complications are present. Nevertheless, CXR is performed in more than 50% of hospitalized patients with bronchiolitis, which exposes infants to ionizing radiation.

Data on the possible role of lung ultrasound (LUS) in children with bronchiolitis and suspected pulmonary complications have not been published yet.

The purpose of this study is to evaluate the use of LUS compared to CXR in diagnosing and monitoring pulmonary complications (pneumonia, pleural effusion, pneumothorax) in children with acute bronchiolitis. The second purpose of the study is to evaluate the correlation between clinical course and ultrasound findings in children with bronchiolitis.

The inclusion of LUS in the diagnostic work-up of bronchiolitis could possibly reduce the misuse of CXR in infants and the exposure to ionizing radiations.

Bronchiolitis is the most common lower respiratory tract infection that affects children younger than 24 months. The diagnosis is clinical and, according to international guidelines, chest x-ray (CXR) should be reserved for cases in which signs of pulmonary complications are present or where respiratory effort is severe to warrant intensive care unit admission. Despite these recommendations, CXR is still performed in about 50% of bronchiolitis (ranging from 24 to 77%), which exposes infants to ionizing radiation.

Given its portability, no ionizing radiation, rapid and repeat testing, lung ultrasound (LUS) has become an emerging diagnostic tool for pneumonia, pleural effusion and pneumothorax in adults and children. At present, LUS is not included in the diagnostic work-up of bronchiolitis. Previous papers have reported that LUS may be useful in bronchiolitis because of a good correlation between clinical course and ultrasound findings. However, data on the possible role of LUS in children with bronchiolitis and suspected pulmonary complications have not been published yet.

Enrolled patients will undergo a bedside LUS in the first 12 hours after CXR. LUS will be performed by one paediatrician with specific LUS expertise and blinded to clinical and radiological data. The paediatrician must have previously attended a specific course on LUS and supervised practical training. A Mindray-DC-T6 ultrasound machine equipped with a linear probe with frequencies ranging from 7.5 to 12 MHz will be use. LUS examination will consist of both longitudinal and transversal sections from the anterior, lateral and posterior chest wall according to the methodology described by Copetti et al. A radiologist will then independently repeat the LUS to test the sonographer inter-observer agreement. The radiologist will be blinded to the results of the previous studies (LUS and CXR). The LUS findings will be recorded on the data form together with patient demographics, symptoms, CXR findings and laboratory data.

Patients with LUS positive for pulmonary complications will receive follow-up ultrasound every 48 hours until the resolution or the discharge.

Inclusion Criteria:

• Children hospitalized with a diagnosis of bronchiolitis
• Age < 24 months
• CXR as part of usual clinical practice because of clinical suspicion of pulmonary complications
• Informed written consent

Exclusion Criteria:

• chronic respiratory disease (i.e. bronchopulmonary dysplasia)
• congenital heart disease
• severe neuromuscular disease
• congenital or acquired immunodeficiency