Cine MRI assessment of motility in the unprepared small bowel in the fasting and fed state: beyond the breath-hold

BackgroundThe symptoms of functional bowel disorders are common in postprandial but investigations are generally undertaken in the fasted state using invasive procedures. MRI provides a noninvasive tool to study the gastrointestinal tract in an unperturbed, fed state. The aim of this study was to develop a technique to assess small bowel motility from cine MRI data in the unprepared bowel in fasting and fed states.MethodsFifteen healthy volunteers underwent a baseline MRI scan after which they consumed a 400 g soup. Subjects then underwent a postprandial scan followed by further scans at regular intervals. Small bowel motility was assessed using single‐slice bTFE cine MRI. An optimized processing technique was used to generate motility data based on power spectrum analysis of voxel‐signal changes with time. Interobserver variability (n = 15) and intra‐observer (n = 6) variability were assessed. Changes in the motility index were compared between fasted and immediate postprandial state.Key ResultsExcellent agreement between observers was seen across the range of motility measurements acquired, with intraclass correlation coefficient (ICC) of 0.979 (P [less than] 0.0001) and Bland‐Altman limits of agreement 95% CI: −28.9 to 45.9 au. Intra‐observer variability was low with ICC of 0.992 and 0.960 (2 observers, P [less than] 0.0001). Changes from the fasted to immediately postprandial state showed an average increase of 122.4% ± 98.7% (n = 15).Conclusions & InferencesThis optimized technique showed excellent inter and intra observer agreement. It was sensitive to changes in motility induced feeding. This technique will be useful to study contractile activity and regional patterns along the gastrointestinal tract under physiological conditions

Magnetic resonance imaging biomarkers of gastrointestinal motor function and fluid distribution

Magnetic resonance imaging (MRI) is a well established technique that has revolutionized diagnostic radiology. Until recently, the impact that MRI has had in the assessment of gastrointestinal motor function and bowel fluid distribution in health and in disease has been more limited, despite the novel insights that MRI can provide along the entire gastrointestinal tract. MRI biomarkers include intestinal motility indices, small bowel water content and whole gut transit time. The present review discusses new developments and applications of MRI in the upper gastrointestinal tract, the small bowel and the colon reported in the literature in the last 5 years

Distinct abnormalities of small bowel and regional colonic volumes in subtypes of irritable bowel syndrome revealed by MRI

OBJECTIVES: Non-invasive biomarkers which identify different mechanisms of disease in subgroups of irritable bowel syndrome (IBS) could be valuable. Our aim was to seek useful magnetic resonance imaging (MRI) parameters that could distinguish each IBS subtypes. METHODS: 34 healthy volunteers (HV), 30 IBS with diarrhea (IBS-D), 16 IBS with constipation (IBS-C), and 11 IBS with mixed bowel habit (IBS-M) underwent whole-gut transit and small and large bowel volumes assessment with MRI scans from t=0 to t=360 min. Since the bowel frequency for IBS-M were similar to IBS-D, IBS-M and IBS-D were grouped together and labeled as IBS non-constipation group (IBS-nonC). RESULTS: Median (interquartile range): fasting small bowel water content in IBS-nonC was 21 (10–42), significantly less than HV at 44 ml (15–70), P<0.01 as was the postprandial area under the curve (AUC) P<0.01. The fasting transverse colon volumes in IBS-C were significantly larger at 253 (200–329) compared with HV, IBS-nonC whose values were 165 (117–255) and 198 (106–270) ml, respectively, P=0.02. Whole-gut transit time for IBS-C was prolonged at 69 (51–111), compared with HV at 34 (4–63) and IBS-D at 34 (17–78) h, P=0.03. Bloating score (VAS 0–10 cm) correlated with transverse colon volume at t=405 min, Spearman r=0.21, P=0.04. CONCLUSIONS: The constricted small bowel in IBS-nonC and the dilated transverse colon in IBS-C point to significant differences in underlying mechanisms of disease

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 intra-subject 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 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 12 participants completed the study: 9 female, mean age 26 years (SD 5) and body mass index 24.8kg/m2 (SD 3.2). All measures consistently increased above baseline following provocation with macrogol. The volume, water content and content mixing had good intra-subject reproducibility (ICC volume=0.84, water content=0.93, mixing=0.79,

Corticotrophin releasing factor increases ascending colon volume after a fructose test meal in healthy humans: a randomised control trial

Background: Poorly absorbed, fermentable carbohydrates can provoke irritable bowel syndrome (IBS) symptoms by escaping absorption in the small bowel and being rapidly fermented in the colon in some susceptible subjects. IBS patients are often anxious and stressed and stress accelerates small bowel transit which may exacerbate malabsorption. Objective: In this study we investigated the effect of intravenous injection of corticotrophin releasing factor (CRF) on fructose malabsorption and the resulting volume of water in the small bowel. Design: We performed a randomised, placebo controlled, cross-over study of CRF versus saline injection in 11 male and 10 female healthy subjects, examining the effect on the malabsorption of a 40 g fructose test meal and its transit through the gut which was assessed by serial Magnetic Resonance imaging (MRI) and breath hydrogen measurement. Orocaecal transit was assessed using the lactose-ureide C13 breath test and the adrenal response to CRF assessed by serial salivary cortisol measurements. Results: (Mean ± SD) CRF injection caused a significant rise in salivary cortisol which lasted 135 minutes. Small bowel water content (SBWC) rose from baseline, peaking at 45 minutes after fructose ingestion while breath hydrogen peaked later at 75 minutes. The area under the curve (AUC) for SBWC from -15 - 135 minutes was significantly lower after CRF versus saline (mean difference [95% CI] 7433 [275, 14591] mL.min, P = 0.04). Ascending colon volume rose after CRF, significantly more for male volunteers than female (P = 0.025). Conclusions: CRF constricts the small bowel and increases fructose malabsorption as shown by increased ascending colon volumes. This mechanism may help to explain the increased sensitivity of some stressed individuals to fructose malabsorption. This trial was registered at ClinicalTrials.gov as NCT0176328

Simultaneous measurement of gastric emptying of a soup test meal using MRI and gamma scintigraphy

Measurement of gastric emptying is of clinical value for a range of conditions. Gamma scintigraphy (GS) has an established role, but the use of magnetic resonance imaging (MRI) has recently increased. Previous comparison studies between MRI and GS showed good correlation, but were performed on separate study days. In this study, the modalities were alternated rapidly allowing direct comparison with no intra-individual variability confounds. Twelve healthy participants consumed 400 g of Technetium-99m (99mTc)-labelled soup test meal (204 kcal) and were imaged at intervals for 150 min, alternating between MRI and GS. The time to empty half of the stomach contents (T1/2) and retention rate (RR) were calculated and data correlated. The average T1/2 was similar for MRI (44 ± 6 min) and GS (35 ± 4 min) with a moderate but significant difference between the two modalities (p ≤0.004). The individual T1/2 values were measured, and MRI and GS showed a good positive correlation (r = 0.95, p ≤ 0.0001), as well as all the RRs at each time point up to 120 min. Gastric emptying was measured for the first time by MRI and GS on the same day. This may help with translating the use of this simple meal, known to elicit reliable, physiological, and pathological gastrointestinal motor, peptide, and appetite response

Gastric motor and sensory function in health assessed by magnetic resonance imaging: Establishment of reference intervals for the Nottingham test meal in healthy subjects

BACKGROUND Current investigations of gastric emptying rarely identify the cause of symptoms or provide a definitive diagnosis in patients with dyspepsia. This study assessed gastric function by magnetic resonance imaging (MRI) using the modular "Nottingham test meal" (NTM) in healthy volunteers (HVs). METHODS The NTM comprises (a) 400 mL liquid nutrient (0.75 kcal/mL) labeled with Gadolinium-DOTA and (b) an optional solid component (12 agar-beads [0 kcal]). Filling sensations were documented. MRI measurements of gastric volume, emptying, contraction wave frequency, and secretion were obtained using validated methods. KEY RESULTS Gastric function was measured in a population of 73 HVs stratified for age and sex. NTM induced moderate satiety and fullness. Labeled fluid was observed in the small bowel in all subjects after meal ingestion ("early-phase" GE). Secretion was rapid such that postprandial gastric content volume was often greater than meal volume (GCV0 > 400 mL), and there was increasing dilution of the meal during the study (P < 0.001). Gastric half-time was median 66-minutes (95% reference interval 35 to 161-minutes ["late-phase" GE]). The number of intact agar beads in the stomach was 7/12 (58%) at 60-minutes and 1/12 (8%) at 120-minutes. Age, bodyweight and sex had measurable effects on gastric function; however, these were small compared to inter-individual variation for most metrics. CONCLUSIONS AND INFERENCES Reference intervals are presented for MRI measurements of gastric function assessed for the mixed liquid/solid NTM. Studies in patients will determine which metrics are of clinical value and also whether the reference intervals presented here offer optimal diagnostic sensitivity and specificity

Alginate and HM-pectin in sports-drink give rise to intra-gastric gelation in-vivo

The addition of gelling polysaccharides to sport-drinks may provide improved tolerability of drinks with high concentration of digestible carbohydrates (CHO), otherwise known to increase the risk of gastro-intestinal complaints among athletes under prolonged exercise. The physico-chemical properties of a drink containing 14 % wt of digestible CHO (0.7:1 fructose and maltodextrin-ratio), 0.2 % wt of HM-pectin / alginate and 0.06 % wt. sodium chloride were examined under in vitro gastric conditions using rheology and large deformation testing. The in-vivo gelling behaviour of the drink was studied using magnetic resonance imaging of subjects at rest together with blood glucose measurements. The in-vivo results confirm gelation of the test drink, with no gel remaining in the stomach at 60 min and blood glucose values were similar to control. The physico-chemical characterisation of the acidified test drink confirms the formation of a weak gel through which low Mw CHO can diffuse

Application of In Vivo MRI Imaging to Track a Coated Capsule and Its Disintegration in the Gastrointestinal Tract in Human Volunteers

Oral specially coated formulations have the potential to improve treatment outcomes of a range of diseases in distal intestinal tract whilst limiting systemic drug absorption and adverse effects. Their development is challenging, partly because of limited knowledge of the physiological and pathological distal gastrointestinal factors, including colonic chyme fluid distribution and motor function. Recently, non-invasive techniques such as magnetic resonance imaging (MRI) have started to provide novel important insights. In this feasibility study, we formulated a coated capsule consisting of a hydroxypropyl methylcellulose (HPMC) shell, coated with a synthetic polymer based on polymethacrylate-based copolymer (Eudragit®) that can withstand the upper gastrointestinal tract conditions. The capsule was filled with olive oil as MRI-visible marker fluid. This allowed us to test the ability of MRI to track such a coated capsule in the gastrointestinal tract and to assess whether it is possible to image its loss of integrity by exploiting the ability of MRI to image fat and water separately and in combination. Ten healthy participants were administered capsules with varying amounts of coating and underwent MRI imaging of the gastrointestinal tract at 45 min intervals. The results indicate that it is feasible to track the capsules present in the gastrointestinal tract at different locations, as they were detected in all 10 participants. By the 360 min endpoint of the study, in nine participants the capsules were imaged in the small bowel, in eight participants in the terminal ileum, and in four in the colon. Loss of capsule integrity was observed in eight participants, occurring predominantly in distal intestinal regions. The data indicate that the described approach could be applied to assess performance of oral formulations in undisturbed distal gastrointestinal regions, without the need for ionizing radiation or contrast agents