[1] Univ Groningen, Univ Med Ctr Groningen, Dept Surg, Anorectal Physiol Lab, Hanzepl 1,pob 30 001, NL-9700 RB Groningen, Netherlands
[2] Univ Groningen, Univ Med Ctr Groningen, Dept Surg, Div Pediat Surg, Groningen, Netherlands
[3] Med Spectrum Twente, Dept Gastroenterol & Hepatol, Enschede, Netherlands