Discussion
In this study, we prospectively addressed the role of LUS in a cohort of children with proven SARS-CoV-2 infection, evaluated in a tertiary level referral center for pediatric COVID-19. Vertical artifacts are the most common signs on LUS, while subpleural consolidations, white lung and pleural effusions are relatively rare, compared to described reports from adult with COVID-19. LUS had a 90.9% sensitivity in detecting signs of lung involvement by COVID-19. Importantly, the LUS allowed to differentiate between those with mild or moderate disease.
In this study, we evaluated the role of LUS in the follow-up of children with COVID-19, a data not yet addressed in current literature. LUS control was performed of day 4 of disease and showed in most cases a resolution or improvement of LUS findings. The improvement in LUS was concordant with the improvement of clinical conditions and laboratory tests, suggesting that LUS can also be used in the monitoring of the disease in children with COVID-19, as also previously suggested in adults with COVID-19 (11,12) and children with other lung infections.19
A recent multicentric, European study described 582 children and adolescents with PCR-confirmed SARS-CoV-2 infection, with a median age of 5 years.20 Majority of children had mild disease, including infants, and 52% of evaluated children had radiologic findings of pneumonia (47%) or acute respiratory distress syndrome (5%). Considering the widely accepted ability of LUS in detecting both pneumonia and ARDS, and the fact that majority of children have a mild disease, our study highlights the possibility of using LUS as a routine and primary level diagnostic in children with stable clinical conditions, reserving secondary level imaging (including CT) to those with diffuse lung disease or with unstable clinical conditions, as previously hypothesized.2
This approach would have several benefits: first of all, would reduce radiation exposure related to the routine use of CT scan, suggested by the Chinese Study group on children with COVID-19; secondly, this approach would allow the same physicians to perform both clinical examination, blood sampling and nasopharyngeal swab, and LUS, during the first clinical examination in the emergency department, reducing the risk of exposure to SARS-CoV-2 of other operators. Third, LUS can be used multiple time and can allow close follow-up of children, potentially directly at home, reducing the pressure on critically overloaded emergency department during the peak of the pandemic.
In this study, only a limited number of children performed chest X-ray or CT scan, therefore we have not been able to compare the different technics. For ethical reasons, the routine use of CT scan for research purposes was not allowed in our Institution, and only those children with more severe disease, or in case of clinical decision of the evaluating doctor, underwent CT scan. Importantly, the use of LUS as the first examination performed in children COVID-19 has allowed to reserve the CT only in selected cases, that is, to those who presented at the first LUS a greater interstitial involvement. In addition, these patients were subjected to closer multiparametric and ultrasound monitoring during the hospitalization, performing ultrasound controls in addition to those defined by the study protocol (T0-T1). In 75% of children enrolled we performed a LUS after 10 days from the negativization of swab for SARS-CoV-2and we found in all a normalization of the lung parenchyma.
Although not showed in the results section, it is important to mention that none of the pediatricians responsible of performing LUS resulted positive to SAR-CoV-2 infection on multiple screening procedures performed within the Institution, confirming that if appropriately performed, LUS is safe also in the context of SARS-CoV-2.