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250 Chapter 12 METHODS Cochrane Library and Medline databases were searched from inception to February 2016. Search terms related to pediatric FC, fiber, pre-, pro- and synbiotics were used. The full search strategy is available from the authors. Studies were eligible for inclusion if they were; 1) (systematic reviews of ) randomizedcontrolled trials (RCTs); 2)written inEnglish; 3) comparing pre-, pro- or synbiotics with placebo, no treatment or any pharmacological therapy for the treatment of FC in children from 0–18 years of age; 4) functional constipation was clearly defined by the authors; 5) reported outcome measures were defecation frequency, fecal incontinence, painful defecation, difficulty with defecation, abdominal pain, quality of life or possible harm from treatment (tolerance, adverse effects). Two authors (I.J.N.K. and M.M.T.) independently assessed the eligibility of all abstracts. In cases of disagreement, consensus was reached through discussion. Additionally, reference lists of included articles were searched. Reasons for exclusion were: 1) treatment arms with < 10 patients; 2) evaluation of a mixture of pre-, pro- or synbiotics with other potentially therapeutic components in the intervention group, to assure that we evaluated the effect of pre- and probiotics only. Quality of evidence was assessed using the Cochrane Collaboration's tool for assessing risk of bias. FIGURE 1. Flowchart of article selection process