Diarrhea management: from pathophysiology to microbiota modulation

Diarrhea, whether acute or chronic, is a common clinical condition with numerous causes that collectively impose significant health, economic, social, and psychological burdens worldwide. Based on its duration, diarrhea is classified as acute when lasting less than 2 weeks and chronic when persisting for more than 4 weeks. From a pathophysiological standpoint, diarrhea can be categorized into four main types: osmotic, secretory, inflammatory, and motility-related. Acute diarrhea is most commonly caused by infectious gastroenteritis and tends to have a self-limited course. In contrast, chronic diarrhea presents a more complex diagnostic challenge due to its varied etiologies and clinical presentations. A shared feature among many causes of both acute and chronic diarrhea is an alteration in the gut microbiota, a condition referred to as dysbiosis. While acute infections often result in temporary microbial imbalance, chronic conditions such as irritable bowel syndrome and symptomatic uncomplicated diverticular disease are associated with persistent dysbiosis. This review aims to explore the most prevalent causes and underlying mechanisms of acute and chronic diarrhea, with a particular focus on the role of the gut microbiota. It will also examine the principal therapeutic strategies aimed at modulating intestinal microbiota, including prebiotics, probiotics, antibiotics, and fecal microbiota transplantation.