Discussion:
Lung US represents a promising method to detect lung abnormalities in adults with COVID-19 pneumonia and its pattern correlates with radiological findings.8-10 At present, only one recent report describes lung US findings in children, reporting high concordance between radiologic and lung US imaging.12In China, where the COVID-19 epidemic started, many children underwent chest X-ray and CT scan of the lung as part of the local diagnostic protocols.5-6,16 The main radiologic findings on CT scan in children with COVID-19 (bronchial thickening, ground-glass opacity, inflammatory lung lesions) were suggestive of pneumonia and were found also in patients with mild symptoms or asymptomatic.16-17 It could be argued that despite the mildness of respiratory symptoms, several children underwent chest CT.6,16 Biologic effects of ionizing radiations are widely known and it is mandatory for pediatricians to choose wisely the best radiologic options balancing clinical conditions and possible adverse events correlated to the diagnostic test.18 As the majority of children with COVID-19 present mild symptoms and complications are rare, CT scan could be reserved to the few severe or complicated pediatric cases. Further to the radiological issues, the risk of transporting COVID-19 patients for CT scan followed by the mandatory decontamination procedure and the risk of nosocomial spread makes this form of imaging risky and time consuming. The diagnostic role of US in several respiratory conditions in children is nowadays widely documented.19 In this COVID-19 outbreak scenario, we pinpoint the usefulness of lung US for the evaluation of infected children. The avowed advantages of lung POCUS in terms of bedside evaluation, absence of radiation, low cost, no need for sedation and the possibility of repeating the examination during follow-up should be exploited and implemented.19-20 Moreover, the possibility of performing lung US by a single operator at the bedside, minimize the need of transferring the patient, consistently reducing the potential risk of further infection spreading within the healthcare personnel.11 Our small series highlighted that lung US clearly documented signs of interstitial pneumonia in a considerable proportion of pediatric patients, which were paucisymptomatic or asymptomatic. When performed, lung US pattern correlated with radiological findings. On subsequent repeated lung US, we found similar findings, but observational time might have been too scarce as patients were mostly discharged a few days after admission. More data are needed to explore whether time interval between symptoms onset and lung US execution modifies ultrasonographic findings. The power of lung US in orientating the management of patients is increased by its correlation with clinical information. Despite the small sample described in our series, we found that lung US can show signs of interstitial pneumonia also in the absence of relevant clinical symptoms. This did not significantly affect clinical management of the patients; therapeutic choices were mostly determined by risky comorbidities. A possible limitation to the spread of lung US is the lack of specific standardized and certified training on lung US. 19-20
The current rapid worldwide spread of SARS-CoV-2 infection requires continual improvement of knowledge about clinical manifestations of COVID-19. As clinical characteristics of pediatric COVID-19 differ from adults, it is of interest to determine whether pediatric lung US shares the same imaging pattern of adults, and whether COVID-19 pneumonia may differ from other virus pneumonias. It could be argued that lung US may be of particular need in guiding therapeutic choices especially for moderate to severe cases. Our study represents a preliminary report of lung US characteristics and usefulness in children affected by COVID-19. Implementation of LUS during the COVID-19 outbreak is of great interest.