Introduction
Initially described in China, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, etiological agent of the Coronavirus Disease 2019 (COVID-19), rapidly spread all over the world being declared a pandemic by the World Health Organization on March 11th, 2020. Although SARS-CoV-2 caused millions of infections and thousands of deaths struggling all health systems worldwide, the impact on children has been relatively milder, with a minority of severe cases and a small number of deaths reported.1 Despite a relatively mild acute COVID-19 in children, the Chinese approach included the routine use of chest Computed Tomography (CT) to all children with SARS-CoV-2 infection no matter the clinical situation.2 However, many studies have proposed a clinically based classification of disease severity for pediatric COVID-19, limiting the use of CT scan to children with severe disease.3-5 The routine use of CT scan to asymptomatic or paucysymptomatic patients can bear risks related to radiation exposure and above all can determine the increase the risk of virus diffusion due to patient displacement from visit room to X-ray room when is in hospital or moving the patient from home to hospital after the discharge.6,7 In this context, lung ultrasound (LUS) can be a useful tool to evaluate lung involvement in children with SARS-CoV-2 infection, since COVID-19 is characterized by peripheral lung lesions easily detected by LUS.8 However, while the role of LUS in adults with COVID-19 has been widely described and a prognostic role has been documented, its use in children is not yet established.9-12 To date, only two small preliminary case series of Italian children with COVID-19 have been published, while the role of LUS in the clinical follow-up of children with COVID-19 and potential implication on the use of CT scan is not yet defined.13,14 For these reasons, we performed a prospective observational study in a pediatric COVID-19 hospital aiming to better clarify the usefulness of LUS in children with COVID-19.