This guideline will focus on key issues related to the diagnosis and management of IBS. Given the complexity of IBS, it is not possible to address all diagnostic and management issues. Clinically relevant questions were developed by a panel of experts who focus their clinical and research efforts on disorders of gut-brain interaction (previously called functional GI disorders). The group formulated 25 key statements that followed the population, intervention, comparator, and outcome format to guide the search for evidence (). These questions were answered by performing a comprehensive international literature search (see methods below). This guideline focuses primarily on the evaluation and management of patients in North America, as not all diagnostic tools (e.g., 23-seleno-25-homotaurocholic acid [SeHCAT]) and medications for IBS (e.g., pinaverium) are available in North America. Over the past decade the US Food and Drug Administration (FDA) has issued guidelines, suggesting that therapies for IBS symptoms be evaluated with an emphasis on global symptom improvement. As such, when applicable, questions were developed with an emphasis on evaluating global response to IBS symptoms for each therapy. An inherent limitation to this approach is that not all therapies were evaluated in double-blind, randomized, placebo-controlled trials with the primary endpoint being an improvement in global IBS symptoms. Where appropriate, this is mentioned in the text. Finally, it is worth noting that the strength of the recommendation, as described below, is based on an overall review of the literature and does not infer or imply that an individual patient may or may not receive benefits from the specific therapy described.Population, intervention, comparator, and outcome statements evaluated in the IBS guidelineaPopulation, intervention, comparator, and outcome statements evaluated in the IBS guidelineaPopulation, intervention, comparator, and outcome statements evaluated in the IBS guidelineaAn individualized literature search was performed for each population, intervention, comparator, and outcome question which involved searching MEDLINE, EMBASE, PubMed, and the Cochrane Controlled Trials Register from inception to February 1, 2020. The search emphasized randomized, placebo-controlled trials with at least 10 subjects and study length ≥4 weeks. Abstracts, case reports, uncontrolled studies, and studies less than 4 weeks in duration were not included. References of articles meeting the search criteria were reviewed for additional relevant studies. Trained GRADE methodologists analyzed the data to assess the quality of evidence and given strength of recommendation. The quality of evidence was expressed as high (estimate of effect is unlikely to change with new data), moderate, low, or very low (estimate of effect is very uncertain). GRADE uses objective reproducible criteria to determine quality of evidence and risk of bias among relevant studies, including evidence of publication bias, unexplained heterogeneity among studies, directness of the evidence, and precision of the estimate of effect (13). A summary of the quality of evidence for the statements is given in . The strength of recommendation is given as either strong (most patients should receive the recommended course of action) or conditional (many patients will have this recommended course of action, but different choices may be appropriate for some patients). In the case of conditional recommendations, a greater discussion is warranted, so that each patient can arrive at a decision based on their values and preferences. The strength of recommendation is based on the quality of evidence and risks vs benefits (14).Summary of quality of evidenceWe used a modified Delphi approach to achieve consensus. Each statement was presented during a monthly phone conference and voted on by all expert authors. Statements were revised and then either presented again on a phone conference or circulated by email. One face-to-face meeting was held. The vote on the final recommendation and quality of evidence for each statement was unanimous. A summary of the recommendations is given in ., Irritable bowel syndrome (IBS) is a highly prevalent, chronic disorder that significantly reduces patients' quality of life. Advances in diagnostic testing and in therapeutic options for patients with IBS led to the development of this first-ever American College of Gastroenterology clinical guideline for the management of IBS using Grading of Recommendations, Assessment, Development, and , Pharmacological management of irritable bowel syndrome with diarrhea (IBS-D) Guideline Eight clinical recommendations to guide the use of FDA-approved and over-the-counter medications for irritable bowel syndrome with predominant diarrhea (IBS-D)..