Alterations of bile acid metabolism in patients with functional bowel disorders: a case-control study.

Introduction: It is assumed that up to 50% of patients with functional bowel disorders with diarrhoea may suffer from bile acid (BA) malabsorption, which is considered as an underrecognized cause of chronic diarrhoea.Aim: To evaluate the indicators of BA metabolism in patients with irritable bowel syndrome (IBS).

Material and methods: The study population included 28 healthy adults (control group), 108 patients with IBS with diarrhoea (IBS-D) and 37 with constipation (IBS-C), aged 18-44 years. All participants were assessed by symptoms questionnaires: VSI and FBDSI. High-performance liquid chromatography - mass spectrometry (HPLC-MS) was used to measure serum and faecal BA (sBA and fBA). Ultra-performance liquid chromatography - mass spectrometry (UPLC-MS) was used to evaluate the relative activity (RA) of gut bacterial bile salt hydrolase (BSH).

Results: Primary sBA in absolute and percentages, total fBA, and primary fBA in absolute and percentages were higher, and secondary sBA and fBA in percentages were lower in the IBS-D group compared to the control and IBS-C groups (p < 0.01). The RA of gut bacterial BSH was lower in IBS-D compared to the control and IBS-C groups (p < 0.01). RA of gut bacterial BSH, secondary sBA and fBA correlated negatively with abdominal pain, bloating, stool frequency, Bristol scale, VSI, and FBDSI (p < 0.05 in all). Total fBA, primary sBA, and fBA correlated positively with the same clinical parameters (p < 0.05 in all).

Conclusions: IBS-D patients had altered parameters of BA metabolism that were associated with the severity of clinical symptoms, disease severity, visceral sensitivity, and stool appearance and frequency.