1. University of Groningen, University Medical Center Groningen, Department of General Practice and Elderly Care Medicine, Groningen, The Netherlands
2. Pelvicum kinderbekkenfysiotherapie, Paediatric Pelvic Physiotherapy, Groningen, The Netherlands
3. University of Groningen, University Medical Center Groningen, Department of Epidemiology, Groningen, The Netherlands
4. Emma Children’s Hospital/Amsterdam UMC—location AMC, Department of Pediatric Gastroenterology and Nutrition, Amsterdam, The Netherlands