Combined MRI, high-resolution manometry and a randomised trial of bisacodyl versus hyoscine show the significance of an enlarged colon in constipation: the RECLAIM study.

Background: Colonic motility in constipation can be assessed non-invasively using MRI.
Objective: To compare MRI with high-resolution colonic manometry (HRCM) for predicting treatment response.
Design: Part 1: 44 healthy volunteers (HVs), 43 patients with irritable bowel syndrome with constipation (IBS-C) and 37 with functional constipation (FC) completed stool diaries and questionnaires and underwent oral macrogol (500-1000 mL) challenge. Whole gut transit time (WGTT), segmental colonic volumes (CV), MRI-derived Motility Index and chyme movement by 'tagging' were assessed using MRI and time to defecation after macrogol recorded. Left colonic HRCM was recorded before and after a 700 kcal meal. Patients then proceeded to Part 2: a randomised cross-over study of 10-days bisacodyl 10 mg daily versus hyoscine 20 mg three times per day, assessing daily pain and constipation.
Results: Part 1: Total CVs median (range) were significantly greater in IBS-C (776 (595-1033)) and FC (802 (633-951)) vs HV (645 (467-780)), p<0.001. Patients also had longer WGTT and delayed evacuation after macrogol. IBS-C patients showed significantly reduced tagging index and less propagated pressure wave (PPW) activity during HRCM versus HV. Compared with FC, IBS-C patients were more anxious and reported more pain. Abnormally large colons predicted significantly delayed evacuation after macrogol challenge (p<0.02), impaired manometric meal response and reduced pain with bisacodyl (p<0.05).Part 2: Bisacodyl compared with hyoscine increased bowel movements but caused more pain in both groups (p<0.03).
Conclusion: An abnormally large colon is an important feature in constipation which predicts impaired manometric response to feeding and treatment responses. HRCM shows that IBS-C patients have reduced PPW activity.
Trial Registration Number: The study was preregistered on ClinicalTrials.gov, Reference: NCT03226145.
Competing Interests: Competing interests: RCS: Grants/research supports: Sanofi-Aventis Deutschland, Nestle Consultant to Enterobiotix. MC: Consultant: Sanofi, Takeda, Biocodex, Mayoly. SMS: honoraria for teaching for the Laborie Group. SAT: grant support from Takeda. Consultancy fees AstraZeneca, Sanofi-Aventis. Share holder Motilent.
(© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY. Published by BMJ Group.)