 The study was articulated in 16 weeks. After recruitment, patients entered a 2 week-run-in phase during which evacuative frequency, stool features and gastrointestinal symptoms were recorded on a daily basis using a questionnairediary provided at the study entry by the physician. At the end of the baseline period, patients returned to the center where information regarding AP characteristics, bowel habits and associated symptoms were recorded using a previously validated interviewer-administered questionnaire for pediatric FGIDs. The Functional Disability Inventory FDI, a second interviewer-administered validated questionnaire was used to assess physical and psychosocial functions and investigate patients QoL. The instrument consists of 15 items concerning perceptions of activity limitations during the past 2 weeks; total scores are computed by summing the ratings for each item. Total available score ranges from 0 to 60 and higher scores indicate greater disability. After completing these questionnaires, patients were assigned in a double-blinded fashion to the placebo or intervention group according to a computer-generated randomization allocation table. Participants were randomized to receive either 1 sachet per day of a mixture of three Bifidobacteria namely, 3 billions of Bifidobacterium longum BB536, 1 billion of Bifidobacterium infantis M-63, and 1 billion of Bifidobacterium breve M-16V, or an identical looking and tasting placebo for six weeks. No further medication other than analgesics was allowed for the whole duration of the study. 