aPediatric Unit, Department of Clinical, Surgical, Diagnostic and Pediatric Sciences, University of Pavia

bPediatric Clinic, Fondazione IRCCS Policlinico San Matteo, Pavia

cDepartment of Woman, Child and General and Specialized Surgery, University of Campania ‘Luigi Vanvitelli’, Napoli, Italy

Correspondence to Professor Gian Luigi Marseglia, Pediatric Unit, Department of Clinical, Surgical, Diagnostic and Pediatric Sciences, University of Pavia, Fondazione IRCCS Policlinico San Matteo, p.le Golgi 19, 27100 Pavia, Italy. Tel: +390382502818; e-mail: [email protected]