[1] Univ Hosp Rostock, Dept Paediat Surg, D-18057 Rostock, Germany
[2] Great Ormond St Hosp Sick Children, Dept Specialist Neonatal & Paediat Surg, Specialist Colorectal Serv, London WC1N 3BH, England
[3] Oslo Univ Hosp, Dept Pediat Surg, N-0372 Oslo, Norway
[4] Klinikum Bremen Mitte, Clin Paediat Surg & Paediat Urol, D-28205 Bremen, Germany
[5] UCL, UCL GOSH Inst Child Hlth, London WC1E 6BT, England
[6] Med Univ Graz, Dept Pediat & Adolescent Surg, A-8036 Graz, Austria