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.

This study aims to utilize intestinal sampling capsules to directly collect small intestinal fluid samples from both IBS patients and healthy controls. The community structure, diversity, and compositional differences of the small intestinal microbiota will be analyzed using 16S rRNA gene sequencing and metagenomic sequencing technologies, while the metabolic profiles of the small intestinal fluid will be detected via untargeted metabolomics.

Inclusion Criteria:

Experimental Group： Aged 18-65 years, male or female. Meets the Rome IV diagnostic criteria for IBS The absence of organic gastrointestinal disease that could explain the symptoms.

Provides informed consent and voluntarily signs the informed consent form. Control Group： Age and sex-matched to the IBS patient group. No history of chronic digestive diseases or current gastrointestinal symptoms. Has not used antibiotics, proton pump inhibitors, probiotics, or other medications known to affect gut microbiota within the past month.

Provides informed consent and voluntarily signs the informed consent form.

Exclusion Criteria:

History of gastrointestinal surgery (excluding appendectomy). Presence of concomitant organic gastrointestinal diseases (e.g., inflammatory bowel disease, celiac disease, gastrointestinal tumors).

Presence of severe concomitant cardiac, hepatic, renal, endocrine, hematologic, or neurological diseases.

Long-term use of medications known to affect gastrointestinal motility (e.g., opioids).

Pregnancy, lactation, or women planning a pregnancy. Conditions contraindicating the use of capsule endoscopy, such as dysphagia, or known gastrointestinal strictures, diverticula, or obstruction.

Any other condition deemed by the investigator as unsuitable for participation in the study.

The cohort included Rome IV-diagnosed IBS patients without confounding surgical or medication history, along with age- and sex-matched healthy controls.