Colonic response to laxative ingestion as assessed by MRI differs in constipated irritable bowel syndrome compared to functional constipation

摘要

Background Functional constipation (FC) and irritable bowel syndrome with constipation (IBS-C) share many symptoms but underlying mechanisms may be different. We have developed a magnetic resonance imaging (MRI) technique to measure intestinal volumes, transit, and motility in response to a laxative, Moviprep (R). We aim to use these biomarkers to study the pathophysiology in IBS-C and FC. Methods Twenty-four FC and 24 IBS-C were studied. Transit was assessed using the weighted average position score (WAPS) of five MRI marker pills, taken 24 h before MRI scanning. Following baseline scan, participants ingested 1 L of Moviprep (R) followed by hourly scans. Magnetic resonance imaging parameters and bowel symptoms were scored from 0 to 4 h. Key Results Weighted average position score for FC was 3.6 (2.5-4.2), significantly greater than IBS-C at 2.0 (1.53.2), p = 0.01, indicating slower transit for FC. Functional constipation showed greater fasting small bowel water content, 83 (63-142) mL vs 39 (15-70) mL in IBS-C, p < 0.01 and greater ascending colon volume (AC), 314 (101) mL vs 226 (71) mL in IBS-C, p < 0.01. FC motility index was lower at 0.055 (0.044) compared to IBS-C, 0.107 (0.070), p < 0.01. Time to first bowel movement following ingestion of Moviprep (R) was greater for FC, being 295 (116-526) min, compared to IBS-C at 84 (49-111) min, p < 0.01, and correlated with AC volume 2 h after Moviprep (R), r = 0.44, p < 0.01. Using a cut-off > 230 min distinguishes FC from IBS-C with low sensitivity of 55% but high specificity of 95%. Conclusion & Inferences Our objective MRI biomarkers allow a distinction between FC and IBS-C.