Demonstration of differences in colonic volumes, transit, chyme consistency, and response to psyllium between healthy and constipated subjects using magnetic resonance imaging

BackgroundIn functional gastrointestinal disorders a lack of objective biomarkers limits evaluation of underlying mechanisms. We aimed to demonstrate the utility of magnetic resonance imaging for this task using psyllium, an effective constipation treatment, in patients and controls. MethodsTwo crossover studies: (i) adults without constipation (controls, n=9) took three treatments in randomized order for 6days - maltodextrin (placebo), psyllium 3.5g t.d.s and 7g t.d.s., (ii) adults with chronic constipation (patients, n=20) took placebo and psyllium 7g t.d.s. for 6days. MRI was performed fasting and postprandially on day 6. Measurements included small bowel and ascending colon water content, colonic volume, transit time, and MR relaxometry (T1, T2) to assess colonic chyme. Stool water percentage was measured. Results7g psyllium t.d.s. increased fasting colonic volumes in controls from median 372mL (IQR 284-601) to 578mL (IQR 510-882), and in patients from median 831mL (IQR 745-934) to 1104mL (847-1316), P<.05. Mean postprandial small bowel water was higher in controls and patients after 7g psyllium t.d.s. vs placebo. Whole gut transit was slower in patients than controls (P<.05). T1 of the descending colon chyme (fasting) was lower in patients (213ms, 176-420) than controls (440ms, 352-884, P<.05) on placebo, but increased by 7g psyllium t.d.s. (590ms, 446-1338), P<.001. Descending colon T1 correlated with baseline stool water content and stool frequency on treatment. Conclusions and InferencesMRI measurements can objectively demonstrate the mode of action of therapy targeting intestinal fluid content in constipation.