[1] Univ Groningen, Univ Med Ctr Groningen, Dept Surg, Sect Pediat Surg, POB 196, NL-9700 AD Groningen, Netherlands
[2] Univ Med Ctr Utrecht, Wilhelmina Childrens Hosp, Dept Pediat Surg, POB 85090, NL-3508 AB Utrecht, Netherlands
[3] Erasmus MC, Sophia Childrens Hosp, Dept Pediat Surg, POB 2040, NL-3000 CA Rotterdam, Netherlands
[4] Univ Amsterdam, Med Ctr, Dept Pediat Surg, POB 22660, NL-1100 DD Amsterdam, Netherlands
[5] Univ Med Ctr Groningen, Dept Epidemiol, POB 196, NL-9700 AD Groningen, Netherlands