Irritable Bowel Syndrome

Dear Colleagues,

Functional gastrointestinal disorders (FGID) comprise the most commonly encountered diagnoses in primary care and gastroenterology clinics and regularly present with a range of abnormalities including intestinal dysmotility, visceral hypersensitivity, altered gastrointestinal mucosal immune function, central nervous system dysregulation, and altered gut microbiota. Accordingly, FGID have been recently defined as disorders of Gut–Brain Interaction associated with the concept of a biopsychological model in the field of neurogastroenterology.

The functional bowel disorder irritable bowel syndrome (IBS) in particular represents a highly prevalent chronic FGID in clinical practice characterized by predominant recurring symptoms or signs of altered bowel habits, bloating, distention in association with abdominal pain. Its global prevalence has been estimated to range from 10% to 20% with significant geographic variations, has a higher prevalence noted in women, and younger people below the age of 50 are more likely to be affected. IBS has a highly significant negative impact on quality of life and represents a substantial economic burden due to high utilization of health care resources and its negative socioeconomic impact on productivity in patients with IBS. The diagnosis of IBS (and other FGID) is based mainly on clinical symptom assessment as most recently outlined in the Rome IV criteria. The diagnostic criteria for IBS consist of the presence of recurrent abdominal pain associated with two or more of the following criteria: 1. related to defecation, 2. associated with a change in frequency of stool, and 3. associated with a change in stool form. Based on the predominant stool consistency, IBS can be grouped into four different subtypes: IBS with predominant diarrhea (IBS-D), with predominant constipation (IBS-C), with mixed bowel habits (IBS-M) and unclassified which has an insufficient abnormality of stool consistency to be in the other groups (IBS-U).

The diagnosis of IBS is therefore based primarily on the presence of particular clinical symptoms and the absence of obvious anatomic or physiologic abnormalities during minimal targeted routine diagnostic evaluation. Furthermore, IBS is not considered to be a single disease entity; it is believed to be a multifactorial syndrome of symptoms with differing underlying causes with environmental and hereditary/genetic factors, dysregulation of the bidirectional communication system between the gastrointestinal tract and the brain (brain–gut axis) associated with disruption of cellular immune responses, the gut microbiota, and the gastrointestinal neuroendocrine system.

The crucial foundation for successful management of IBS patients is the development of a trusted patient provider relationship that ultimately can result in improved outcomes. Treatment modalities are directed to alleviate predominant IBS symptoms and may include dietary, non-pharmacological, and targeted pharmacological interventions and also psychological therapy options. The ongoing advance of the fundamental understanding of the gut microbiome and the complexity of the brain–gut axis will undoubtedly uncover further opportunities of additional IBS treatment modalities in the near future.

This special edition on IBS presents several expert reviews on a broad range of important aspects related to the current understanding of the pathophysiology, clinical diagnosis, and management of the functional bowel disorder irritable bowel syndrome.

Dr. H. Christian Weber, MD
Guest Editor

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