Gut Microbiota Characterization in Fecal Incontinence and Irritable Bowel Syndrome

Anal incontinence (AI) is defned as the inability to delay evacuation until socially convenient (urge incontinence) or, more in general, as the involuntary passage of gut contents through the anus (passive incontinence or soiling/fecal seepage, the latter defning leakage of stool or mucus that occurs with normal continence and evacuation) [1]. Its prevalence is likely underestimated, due to embarrassment. Although it is known to increase with age, young individuals can also be affected, with no differences between males and females. Numerous idiopathic or secondary neuromuscular disorders of the pelvic foor and/or anal sphincter and/or rectum can be involved in causing its onset and are extensively described in this volume. Although diarrhea is more likely associated with incontinence, also severe constipation with fecal impaction and related pseudo-diarrhea can precipitate borderline anatomical and functional anorectal abnormalities. The irritable bowel syndrome (IBS) is the most frequent clinical condition characterized by bowel abnormalities including diarrhea (IBS-D), constipation (IBS-C) and mixed bowel habits (IBS-M) [2]. AI has been reported to affect 15–20% of patients with IBS in a multicenter study [3]. Similarly, fecal incontinence occurring at least once per week was reported in 20% of IBS patients in a single-center study from the UK [4]. Compared with those who did not report AI, IBS patients affected by this severe complication had more frequently IBS-D, had undergone more gastroenterological consultations, and they were older, more frequently males, with higher body mass index and, not surprisingly, had more anxiety and depression [4]. Still, these fgures could be markedly underestimated, since a prevalence as high as 60% was reported in another study carried out at a secondary care level in the UK and one-fourth of included patients admitted never having disclosed their incontinence before [5]. Appropriate management of IBS is required to control incontinence in affected individuals. We will briefy summarize the current view on IBS with a specifc focus on the role of changes and modulation of gut microbiota.