Efficacy and Safety of Lactobacillus reuteri DSM 17938 in Pediatric Functional Abdominal Pain Disorders: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background/Objective: Lactobacillus reuteri DSM 17938 is among the most studied probiotic strains for pediatric functional abdominal pain disorders (FAPDs), but prior trials and systematic reviews have reached inconsistent conclusions. This systematic review and meta-analysis aimed to evaluate the efficacy and safety of L. reuteri DSM 17938 in children and adolescents with FAPDs. Methods: This review was registered in PROSPERO (CRD42024618099). PubMed, Cochrane Library, Embase, Web of Science, Scopus, CINAHL, and LILACS were searched from inception to 8 April 2026, for randomized controlled trials (RCTs) enrolling children ≤ 18 years with Rome III/IV-defined FAPDs receiving L. reuteri DSM 17938 versus placebo. Random-effects meta-analyses were performed for pain severity, pain frequency, quality of life, and adverse events; risk of bias was assessed with RoB 2 and certainty of evidence with GRADE. Results: Seven RCTs (513 participants) were included. Pain severity showed no significant difference at end of follow-up (SMD −0.58; 95% CI −1.32 to 0.16; I² = 89.3%) but a significant reduction at end of treatment (SMD −0.49; 95% CI −0.93 to −0.06; p = 0.027; I² = 82.0%), an effect not robust to sensitivity analysis. Pain frequency showed no significant difference at end of follow-up (MD −0.15 episodes/week; 95% CI −1.18 to 0.87) or end of treatment. No trial assessed quality of life. Adverse events were reported narratively only. Certainty of evidence was very low for pain outcomes and low for adverse events. Conclusions: Current evidence does not support a consistent beneficial effect of L. reuteri DSM 17938 on pain severity or frequency in pediatric FAPDs, and safety data remain limited. Certainty of evidence was low to very low across outcomes, underscoring the need for larger, methodologically rigorous trials.