| Summary: | 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®. 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® 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 (1.5–3.2), 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® 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 = 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.
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