Bowel Sound Feature-Based Stimulus/Response Plots to Differentiate Healthy Controls From Functional Constipation and Functional Diarrhea: A Cross-Sectional Study

Functional constipation (FC) and functional diarrhea (FD), which belong to the functional gastrointestinal disorders group, are primarily associated with abnormalities in intestinal motility and can result in chronic abdominal symptoms. However, because diagnoses are largely based on subjective evaluations, objective diagnostic indicators need to be established. In this study, a novel method is proposed for quantitatively evaluating characteristic intestinal motility patterns in FC and FD patients by using bowel sounds (BSs) to create stimulus–response plots. BSs were recorded before and after carbonated water ingestion in healthy individuals and patients diagnosed with FC or FD according to the Rome IV criteria, and these recordings were used to construct stimulus–response plots. For healthy individuals, there was a strong negative correlation (R = –0.8676, p <0.001) between the number of BS segments before and after ingestion, whereas no statistically significant correlation was observed in the FC/FD group. Furthermore, approximately 25% of measurements for the healthy group deviated from the region defined by a distance of 0.8217 from the healthy group regression line, compared with approximately 55% for those in the FC/FD group, suggesting a substantial difference in BS patterns. These findings indicate that some FC/FD patients may exhibit abnormal intestinal motility patterns upon ingesting carbonated water. In conclusion, the results of this study suggest that the proposed method has potential as a new objective evaluation tool to complement current diagnostic approaches, which rely heavily on subjective assessment.