MRI tagging of colonic chyme mixing in healthy subjects: Inter-observer variability and reliability of the measurement with time.

BACKGROUND: Magnetic resonance imaging (MRI) tagging techniques have been applied to the GI tract to assess bowel contractions and content mixing. We aimed to evaluate the dependence of a tagging measurement (for assessing chyme mixing) on inter-observer variability in both the ascending colon (AC) and descending colon (DC) and to investigate the temporal variation and hence reliability of the colonic tagging technique by acquiring multiple measurements over time on healthy participants. METHODS: Two independent datasets of healthy adults were used for the retrospective inter-observer variability (Study 1: 13 datasets and Study 2: 31 datasets), and ten participants were scanned for the prospective temporal variation study following a 1 L mannitol oral preparation. All colonic tagging data were acquired on 3 T MRI scanners. The mean and the standard deviation (SD) maps were generated pixel-by-pixel using custom-written software in MATLAB. The colonic regions of interest were defined using MIPAV software. Bland-Altman plots and scatter plots were used for the inter-observer variability. The mean and SD of all repeated measures for each subject were calculated along with a one-way ANOVA to test for variations with time. RESULTS: Scatter plots and Bland-Altman plots showed a large range of data with low variation and small limits of agreements (<5% CoV). The intraclass correlation coefficient of inter-rater reliability was excellent and 0.97 or above for the AC and DC measurements for both datasets. The temporal variation study shows that there was no significant difference found between the multiple measures with time (p = 0.53, one-way repeated measures ANOVA test). CONCLUSIONS: MRI tagging technique can provide an assessment of colonic chyme mixing. The inter-observer study data showed high inter-rater agreement. The temporal variation study showed some individual variations with time suggesting multiple measurements may be needed to increase accuracy.

Test-retest assessment of non-contrast MRI sequences to characterise and quantify the small bowel wall in healthy participants.

OBJECTIVE: Quantitative Magnetic Resonance Imaging sequences have been investigated as objective imaging biomarkers of fibrosis and inflammation in Crohn's disease. AIM: To determine the repeatability and inter- and intra-observer agreement of these measures in the prepared small bowel wall. METHODS: Ten healthy participants were scanned at 3 T on 2 separate occasions using T1 and T2 relaxometry, IVIM-DWI and MT sequences. Test-retest repeatability was assessed using the coefficient of variation (CoV) and intra-class correlation coefficients (ICCs) were used to evaluate the intra- and inter-observer agreement RESULTS: Test-retest repeatability in the bowel wall was excellent for apparent diffusion coefficient (ADC), magnetisation transfer ratio (MTR), T1, and diffusion coefficient D (CoV 5%, 7%, 8%, and 10%, respectively), good for perfusion fraction (PF) (CoV 20%) and acceptable for T2 (CoV 21%). Inter-observer agreement was good for the T2, D and ADC (ICC = 0.89, 0.86, 0.76, respectively) and moderate for T1 (ICC = 0.55). Intra-observer agreement was similar to inter-observer agreement. DISCUSSION: This study showed variable results between the different parameters measured. Test-retest repeatability was at least acceptable for all parameters except pseudo-diffusion coefficient D*. Good inter- and intra-observer agreement was obtained for T2, ADC and D, with these parameters performing best in this technical validation study.

Contrasting effects of viscous and particulate fibers on colonic fermentation in vitro and in vivo, and their impact on intestinal water studied by MRI in a randomized trial.

BACKGROUND: Wheat bran, nopal, and psyllium are examples of particulate, viscous and particulate, and viscous fibers, respectively, with laxative properties yet contrasting fermentability. OBJECTIVES: We assessed the fermentability of these fibers in vitro and their effects on intestinal function relevant to laxation in vivo using MRI. METHODS: Each fiber was predigested prior to measuring gas production in vitro during 48-h anaerobic incubation with healthy fecal samples. We performed a randomized, 3-way crossover trial in 14 healthy volunteers who ingested 7.5 g fiber twice on the day prior to study initiation and once with the study test meal. Serial MRI scans obtained after fasting and hourly for 4 h following meal ingestion were used to assess small bowel water content (SBWC), colonic volumes, and T1 of the ascending colon (T1AC) as measures of colonic water. Breath samples for hydrogen analysis were obtained while patients were in the fasted state and every 30 min for 4 h following meal ingestion. RESULTS: In vitro, the onset of gas production was significantly delayed with psyllium (mean ± SD: 14 ± 5 h) compared with wheat bran (6 ± 2 h, P = 0.003) and was associated with a smaller total gas volume (P = 0.01). Prefeeding all 3 fibers for 24 h was associated with an increased fasting T1AC (>75% of values >90th centile of the normal range). There was a further rise during the 4 h after psyllium (0.3 ± 0.3 s P = 0.009), a fall with wheat bran (-0.2 ± 0.2 s; P = 0.02), but no change with nopal (0.0 ± 0.1 s, P = 0.2). SBWC increased for all fibers; nopal stimulated more water than wheat bran [AUC mean (95% CI) difference: 7.1 (0.6, 13.8) L/min, P = 0.03].Breath hydrogen rose significantly after wheat bran and nopal but not after psyllium (P < 0.0001). CONCLUSION: Both viscous and particulate fibers are equally effective at increasing colonic T1 over a period of 24 h. Mechanisms include water trapping in the small bowel by viscous fibers and delivery of substrates to the colonic microbiota by more fermentable particulate fiber. This trial was registered at clinicaltrials.gov as NCT03263065.

The MRI colonic function test: Reproducibility of the Macrogol stimulus challenge.

BACKGROUND: Magnetic resonance imaging (MRI) of the colonic response to a macrogol challenge drink can be used to assess the mechanisms underlying severe constipation. We measured the intrasubject reproducibility of MRI measures of colonic function to aid their implementation as a possible clinical test. METHODS: Healthy participants attended for MRI on two occasions (identical protocols, minimum 1 week apart). They underwent a fasted scan and then consumed the macrogol drink. Subjects were scanned at 60 and 120 minutes, with maximum value reached used for comparison. The colonic volume, water content, mixing of colonic content and the movement of the colon walls were measured. Coefficients of variation and intraclass correlation coefficients (ICC) were calculated. RESULTS: Twelve participants completed the study: nine female, mean age 26 years (SD 5) and body mass index 24.8 kg/m2 (SD 3.2). All measures consistently increased above baseline following provocation with macrogol. The volume, water content and content mixing had good intrasubject reproducibility (ICC volume = 0.84, water content = 0.93, mixing = 0.79, P < .001). With the wall movement, the response to the challenge was generally large, but more variable between visits resulting in a lower ICC overall (ascending colon = 0.65, descending colon = 0.76, P < .001). CONCLUSIONS: The colonic response to the macrogol stimulus as assessed by MRI is heterogeneous but large compared to baseline, with moderate to good reproducibility, making the test suitable to study potential pathologies underlying GI disorders such as constipation. More data are needed to better define the normal range for comparison with patient groups who may have both hypo- and hypermotile responses.

Mechanisms underlying effects of kiwifruit on intestinal function shown by MRI in healthy volunteers.

BACKGROUND: Chronic constipation affects approximately 17% of the population worldwide and remains an important unmet need since patients are often dissatisfied with treatment. Kiwifruit may offer an alternative to traditional laxatives and have been shown to increase stool volume, frequency and improve consistency. AIMS: Using non-invasive MRI techniques, we assessed the effect of ingestion of kiwifruit on fluid distribution in the intestines and bowel function. METHODS: Two period crossover trial of kiwifruit vs control in healthy adults. INTERVENTION: two kiwifruits twice daily vs isocaloric control (maltodextrin) twice daily, consumed for a total of 3 days. Subjects underwent MRI scanning fasted and at hourly intervals for 7 hours on the third day. PRIMARY OUTCOME: T1 relaxation time of ascending colon (T1AC) using MRI. SECONDARY OUTCOMES: Small bowel water content (SBWC), colonic volume, gut transit time, T1 of descending colon, stool frequency and form. RESULTS: Fourteen volunteers completed the study. T1AC was higher after kiwifruit ingestion (P = 0.029) during the second half of the day (when meal residue would be expected to reach the AC, AUC T1 T240-420 minutes; mean (SD) 137 (39) s*minute with kiwifruit versus 108 (40) s*minute with control. SBWC (P < 0.001), colon volumes (P = 0.004), as well as stool frequency (1.46 ± 0.66 with kiwifruit vs 1.14 ± 0.46 stools per day with control; P = 0.034) and stool form score (Bristol Stool Chart score 4.1 (0.9) with kiwifruit versus 3.4 (0.7) with control; P = 0.011) were markedly increased in participants consuming kiwifruit compared to control. CONCLUSION: Consumption of kiwifruit in healthy volunteers increases water retention in the small bowel and ascending colon and increases total colonic volume. The data may explain the observed increase in stool frequency and looser stool consistencies, suggesting that kiwifruit could be used as a dietary alternative to laxatives in mild constipation.

Results of the British Society of Gastroenterology supporting women in gastroenterology mentoring scheme pilot.

INTRODUCTION: Mentorship has long been recognised as beneficial in the business world and has more recently been endorsed by medical and academic professional bodies. Recruitment of women into gastroenterology and leadership roles has traditionally been difficult. The Supporting Women in Gastroenterology network developed this pilot scheme for female gastroenterologists 5 years either side of the Completion Certificate of Specialist Training (CCST) to examine the role that mentorship could play in improving this discrepancy. METHOD: Female gastroenterology trainees and consultant gastroenterologists within 5 years either side of CCST were invited to participate as mentees. Consultant gastroenterologists of both genders were invited to become mentors. 35 pairs of mentor:mentees were matched and completed the scheme over 1 year. Training was provided. RESULTS: The majority of the mentees found the sessions useful (82%) and enjoyable (77%), with the benefit of having time and space to discuss professional or personal challenges with a gastroenterologist who is not a colleague. In the longitudinal study of job satisfaction, work engagement, burnout, resilience, self-efficacy, self-compassion and work-life balance, burnout scale showed a small but non significant improvement over the year (probably an effect of small sample size). Personal accomplishment improved significantly. The main challenges were geography, available time to meet and pair matching. The majority of mentors surveyed found the scheme effective, satisfying, mutually beneficial (70%) and enjoyable (78%). CONCLUSION: Mentorship is shown to be beneficial despite the challenges and is likely to improve the recruitment and retention of women into gastroenterology and leadership roles, but is likely to benefit gastroenterologists of both genders.

Insights Into the Different Effects of Food on Intestinal Secretion Using Magnetic Resonance Imaging.

BACKGROUND: Plant foods may stimulate intestinal secretion through chemicals designed to deter herbivores, including lactucins in lettuce and rhein in rhubarb. This may increase ileostomy output and induce diarrhoea in people with intact bowels. OBJECTIVE: We aimed to determine the effect of food on intestinal water content using Magnetic Resonance Imaging (MRI). DESIGN: A three period crossover trial of isocaloric meals in adults without bowel disorders. Meals: 2 slices white bread with 10 g butter; 300 g rhubarb with 60 mL lactose free cream; 300 g lettuce with 30 mL mayonnaise. PRIMARY OUTCOME: Area under curve (AUC) small bowel water content (SBWC) using MRI. SECONDARY OUTCOMES: ascending colon water content; T1 relaxation time of ascending colon (T1AC); gastric volume; visual analogue scales of bloating and satiety (0-100). MRI analysts were blinded. Scanned fasting and hourly to 180 min postprandial. Symptoms scored half-hourly. RESULTS: 9 female and 6 male subjects completed the study. AUC SBWC fell after bread but rose after lettuce and even more after rhubarb, difference from baseline being (Bread AUC -5662 (1209) ml.min vs Lettuce 3194 (1574) ml.min and Rhubarb 10586 (1629) ml.min (P < 0.01). Rhubarb induced a rise in T1AC but differences at 3 hours were not significant (P = 0.06). Gastric volume at T = 0 significantly was higher for both lettuce and rhubarb (571 ± 92 and 558 ± 89 mls) respectively compared to bread (314 ± 108 mls) (p < 0.0001). Symptom scores were higher for lettuce > rhubarb > bread. CONCLUSION: Lettuce and rhubarb meals increased intestinal water content, demonstrating how different foods can alter ileal flow and stool consistency.

Differential effects of FODMAPs (fermentable oligo-, di-, mono-saccharides and polyols) on small and large intestinal contents in healthy subjects shown by MRI.

OBJECTIVES: The objective of this study was to investigate whether ingestion of fructose and fructans (such as inulin) can exacerbate irritable bowel syndrome (IBS) symptoms. The aim was to better understand the origin of these symptoms by magnetic resonance imaging (MRI) of the gut. METHODS: A total of 16 healthy volunteers participated in a four-way, randomized, single-blind, crossover study in which they consumed 500 ml of water containing 40 g of either glucose, fructose, inulin, or a 1:1 mixture of 40 g glucose and 40 g fructose. MRI scans were performed hourly for 5 h, assessing the volume of gastric contents, small bowel water content (SBWC), and colonic gas. Breath hydrogen (H2) was measured and symptoms recorded after each scan. RESULTS: Data are reported as mean (s.d.) (95% CI) when normally distributed and median (range) when not. Fructose increased area under the curve (AUC) from 0-5 h of SBWC to 71 (23) l/min, significantly greater than for glucose at 36 (11-132) l/min (P<0.001), whereas AUC SBWC after inulin, 33 (17-106) l/min, was no different from that after glucose. Adding glucose to fructose decreased AUC SBWC to 55 (28) l/min (P=0.08) vs. fructose. Inulin substantially increased AUC colonic gas to 33 (20) l/min, significantly greater than glucose and glucose+fructose (both P<0.05). Breath H2 rose more with inulin than with fructose. Glucose when combined with fructose significantly reduced breath H2 by 7,700 (3,121-12,300) p.p.m./min relative to fructose alone (P<0.01, n=13). CONCLUSIONS: Fructose but not inulin distends the small bowel with water. Adding glucose to fructose reduces the effect of fructose on SBWC and breath hydrogen. Inulin distends the colon with gas more than fructose, but causes few symptoms in healthy volunteers.