1. Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland
2. Department of Gastroenterology, Hepatology and Nutrition Disorders, The Children's Memorial Health Institute, Warsaw, Poland
3. Department of Paediatric Endoscopy and Gastrointestinal Function Testing, Nicolaus Copernicus University in Toruń, Ludwik Rydygier Collegium Medicum in Bydgoszcz, Bydgoszcz, Poland
4. Department of Pediatrics, Gastroenterology and Allergology, Medical University of Białystok, Białystok, Poland
5. Second Department of Pediatrics, Gastroenterology and Nutrition, Medical University of Wrocław, Wrocław, Poland
6. Department of Pediatrics, Division of Gastroenterology, Silesian Center for Child Health, Independent Public Clinical Hospital No. 6, Medical University of Silesia, Katowice, Poland
7. First Department of Paediatric, Department of Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznań, Poland
8. Department of Pediatrics, Gastroenterology and Rheumatology, Pomeranian Medical University, Szczecin, Poland