The Study of Nutrition of Children and Adolescents With GERD

Inclusion Criteria: * Willingness to participate (written informed consent and consent from parents or legal representative according to the local law); * Age 6 to 17 years old inclusive, * Possibility to assess symptoms, data of the medical history and receive answers to the questions about usual diet. Exclusion Criteria: * history of abdominal surgery; * presence of varicose veins of the stomach and/or the oesophagus either in medical history or found during the study; * inability to tolerate at least one of the invasive procedures or lacking data of the other instrumental examinations required by protocol; * general condition of the patient making impossible to perform all the examinations or when performing the procedures is not safe and reasonable based on the opinion of the investigator that it may exacerbate the disease flow or put the patient at risk; * intake of medications which may influence the clinical and instrumental data, including, but not limited to: non-steroid anti-inflammatory agents, glucocorticosteroids (except for skin products, if they were used for 2 weeks or less at the time of inclusion into the study), medications affecting adrenergic, acetylcholine receptors, antidepressants, tranquillizers, sedatives, those with known local irritant effect on the gastrointestinal tract mucosa; the use of proton pump inhibitors and H2 receptors blockers are not allowed during the study, a wash-out period for at least 2 weeks is necessary before the enrolment.