Irritable Bowel Syndrome (IBS) is a common functional bowel disorder with complex and not yet fully elucidated pathophysiological mechanisms. Recent research suggests that gut microbiota dysbiosis, particularly small intestinal bacterial overgrowth (SIBO), may play a key role in the generation of IBS symptoms. However, the vast majority of current studies have focused on fecal samples, which primarily reflect the colonic microbiota. The small intestinal microbiota, which is directly involved in nutrient digestion and absorption and more prone to dysbiosis, remains understudied due to the challenges in obtaining samples.