Fasting and postprandial volumes of the undisturbed colon: normal values and changes in diarrhea‐predominant irritable bowel syndrome measured using serial MRI

Abstract

Key Messages• Previous measurements of regional colonic volume have used invasive methods that could disturb natural morphology.• Using MRI, volume measurement of the undisturbed colon was achieved in 75 healthy volunteers and 25 IBS-D patients. Normal volume ranges were defined.• IBS-D patients showed less ability to accommodate post-prandial inflow in the ascending colon. AbstractBackground Previous assessments of colon morphology have relied on tests which were either invasive or used ionizing radiation. We aimed to measure regional volumes of the undisturbed colon in healthy volunteers (HV) and patients with diarrhea-predominant irritable bowel syndrome (IBS-D). Methods 3D regional (ascending, transverse, and descending) colon volumes were measured in fasting abdominal magnetic resonance (MR) images of 75 HVs and 25 IBS-D patients. Thirty-five of the HV and all 25 IBS-D subjects were fed a standard meal and postprandial MRI data obtained over 225 min. Key Results Colonic regions were identified and 3D maps from cecum to sigmoid flexure were defined. Fasted regional volumes showed wide variation in both HVs being (mean AE SD) ascending colon (AC) 203 AE 75 mL, transverse (TC) 198 AE 79 mL, and descending (DC) 160 AE 86 mL with no difference from IBS-D subjects (AC 205 AE 69 mL, TC 232 AE 100 mL, and DC 151 AE 71 mL, respectively). The AC volume expanded by 10% after feeding (p = 0.007) in the 35 HV possibly due to increased ileo-colonic inflow. A later rise in AC volume occurred from t = 90 to t = 240 min as the meal residue entered the cecum. In contrast, IBS-D subjects showed a much reduced postprandial response of the AC (p < 0.0001) and a greater increase in TC volume after 90 min (p = 0.0244) compared to HV. Conclusions & Inferences We have defined a normal range of the regional volumes of the undisturbed colon in fasted and fed states. The AC in IBS-D appeared less able to accommodate postprandial inflow which may account for faster colonic transit.

Quantification and variability in colonic volume with a novel magnetic resonance imaging method

“…The inter-individual variability tallies with the recent findings by Pritchard and colleagues, who found a similar wide variation between subjects. 11 Moreover, MRI assessments before and after defecation displayed a significant volume reduction after defecation in rectosigmoid and total colorectal volume, whereas volumes for cecum/ascending, transverse, and descending colon remained relatively stable. The observed reduction in rectosigmoid colon and total colorectal volumes was associated with the true fecal volume, which reflects the capacity of the present technique to detect significant changes in colorectal volumes.…”

“…32 Similarly, Pritchard and colleagues investigated the fasting and postprandial volumes of the human colon and found, that the cecum/ascending colon volume was subject to a significant postprandial expansion of 10-20% immediately after feeding. 11 To minimize the effect of these factors, the subjects were scanned in a fasting state at the same time of day on both observations and the inclusion and exclusion criteria ensured a homogenous study population. Still, the inter-individual variability was inconsistent across different colorectal segments with the cecum/ascending colon exhibiting the most variability, potentially reflecting its capacity to receive and accommodate content arriving from the small intestine and store it until moved distally by a mass-movement.…”

“…[8][9][10] Magnetic resonance imaging (MRI) allows quantification of segmental colorectal volumes without contrast-enhancing agents and bowel preparation. This can be used to characterize healthy physiology or patient groups 11 or be used in interventional studies. 12 To reduce time expenditure on analysis, semi-automatic and automatic techniques have been developed to determine volumes with MRI, although these are often guided by the use of contrast-enhancing agents, which prevents assessment of resting volume.…”

Colon Hypersensitivity to Distension, Rather Than Excessive Gas Production, Produces Carbohydrate-Related Symptoms in Individuals With Irritable Bowel Syndrome

“…The 'large bowel' hypothesis proposes that rapid colonic fermentation of unabsorbed carbohydrates generates gas, distending the colon and causing flatulence, bloating and discomfort. Reports that some IBS patients have different microbiota to non-sufferers 10,11 , and that the microbiota changes with diet, 12,13 20,21 . Luminal gas has been assessed in both the small bowel 22 and colon 23 .…”

“…The methods for measurement of SBWC and colonic volume have been described in detail previously 17,20 . The sigmoid colon, is normally collapsed and not included in the measurement of the descending colon, however in this study it was noted to often be markedly distended and so was measured by our usual technique, as has recently been shown to be feasible by other groups 32 .…”