Irritable bowel syndrome with diarrhea: Treatment is a work in progress

Irritable bowel syndrome (IBS) is a heterogeneous functional disease with a high prevalence and significant impact on quality of life. Traditionally understood as a pure disorder of brain-gut interaction, it is increasingly clear that IBS encompasses diverse pathologies, some of which involve objective alterations of intestinal structure, function, and the microbiome. IBS is subclassified as diarrhea, constipation, or mixed type based on the most prominent stool form. We review the diagnosis and management of the diarrheal type through a pathophysiologic lens, with attention to recent developments that can inform a mechanistically based targeted approach to treatment.