The aim of the study is to investigate the effect of L. reuteri DSM 17938 on pain frequency and severity in children of 5-16 years old and with diagnosis of FAP.

This is a randomized, double-blind, placebo-controlled study. Subjects between of 5-16 years of age with FAP as defined in the Rome III criteria and with pain severity of at least 40 mm on a 100 mm VAS scale and pain frequency of at least 1 episode per week over the preceding 8 weeks will be recruited. In accordance to the specific Rome III criteria for inclusion, FAP is defined as a variable combination of chronic or recurrent gastrointestinal symptoms not explained by structural or biochemical abnormalities.

A study questionnaire to record pain and other gastrointestinal symptoms will be used.

One-hundred and six (106) Subjects will be randomized to receive either dietary supplementation with L. reuteri DSM 17938 (2 chewable tablets with breakfast), or the same number of comparable placebo tablets, for 4 weeks. Supplementation will be stopped after 4 weeks, and the subjects will be followed up for an additional 4 weeks. The subjects will complete a diary to record frequency and intensity of pain, use of medication, deviation from the usual diet, physical activities, and absence from school and other activities. Gastrointestinal symptoms are assessed by the GSRS (Gastrointestinal Symptom Rating Score).

Subjects/caregivers will be instructed to maintain the usual diet throughout the study, but not to consume other probiotics (foods or supplements) during the entire study period.

The symptoms diary will be completed daily by the parents and will report information on the frequency of pain episodes, location of pain, presence or absence of associated symptoms, need to take medication for pain and interference with normal activities. The intensity of the symptoms will be assessed by using the Wong-Baker Faces scale.

Inclusion Criteria:

Subjects will be recruited according to the following inclusion criteria:

• FAP (Functional Abdominal Pain) according to Rome III criteria for Child/Adolescent; 1 or more abdominal pain episodes per week over the past 8 weeks
• Informed consent by study participant and at least one parent/legal guardian;
• Age of 5-16 years;
• Pain severity at study entry must be at least 40 mm on a 100 mm VAS scale;
• Pain frequency of at least 1 or more episodes per week over the preceding 8 weeks;
• Ability to understand and comply with the requirements of the trial;
• Stated availability throughout the study period

Exclusion Criteria:

Subjects presenting with one or more of the following criteria will be excluded from participation in the study:

• Chronic illness;
• Surgery of gastrointestinal tract
• Any symptoms/signs of organic disease and/or any abnormal results of laboratory assays (total blood count, serum glucose, urea, electrolytes, amylase, SGOT, SGPT, anti tTG antibodies, breath H2 test, suggesting disease other than FAP;
• Weight loss of 5% or more in body weight over the preceding 3 months;
• Exposure to any drugs for FAP in the past 2 weeks.
• Exposure to probiotics or antibiotics within 4 weeks prior to study; subjects can be included following a wash-out period of 4 weeks.
• Participation in other interventional clinical trials in the past 3 months;
• Subjects with special dietary needs