Last update and review: October 19, 2020.
A short summary.
In his 2016 article (1), Robin Spiller provides several new insights into symptom mechanisms and advances in treatment of irritable bowel syndrome (IBS).
Here, we share some of our notes on how magnetic resonance imaging allows a better understanding of intestinal motility in health and disease.
New insights from magnetic resonance imaging of the colon and small intestine.
Spiller, 2016 (1):
Magnetic resonance imaging (MRI) provides a unique opportunity to image the undisturbed gut, since by using a range of sequences adequate contrast can be obtained with normal gut contents 29 . Such studies have provided for the first time accurate assessments of small bowel and regional colonic volumes in normal subjects. The resting small bowel contains surprisingly little free water, varying in different studies from 50 ml 30 to 150 ml 31 . This rises rapidly to around 400 ml after an osmotic stress such as that provided by mannitol 30 or fructose 32 or falls when readily absorbable fluids are provided such as sucrose and glucose 30 . High-fat meals, by contrast, cause a rapid rise in small bowel water content probably due to stimulation of pancreatic obiliary secretions 33 . MRI has shown that there is a very wide normal range of colonic volumes with the ascending colon being mean (standard deviation [SD]) 203 (75) ml, transverse colon 232 (100) ml, and descending colon 151 (71) ml, with total colonic volumes being 632 (167) ml.
95% of patients with IBS-C had colonic volumes within the normal range.
Spiller, 2016 (1):
While IBS-D patients have fasting colonic volumes within the normal range, those with functional constipation have significantly increased ascending colon and total colon volumes at 597 (170) and 1505 (387) ml, respectively 34 . Interestingly, by contrast, 95% of patients with IBS-C had colonic volumes within the normal range. In addition to fasting scans, it is simple to assess the response to feeding and also to a stronger stimulus provided by the osmotic laxative Moviprep R using cine MRI. This shows marked impairment of colonic motility in functional constipation but not IBS-C (Figure 1) 34 . The technique can also be used to show the mode of action of therapeutic agents including Movicol, loperamide, ondansetron, and ispaghula and could be useful in the future when screening drugs designed to alter colonic transit 29 .
Analysis: Before using drugs, explore natural ways to correct IBS-D (diarrhea) and IBS-C (constipation).
One of the therapeutic agents mentioned by Spiller, 2016 (1), in the citation above is Movicol.
The patient leaflet does not mention any significant toxicity and sais Movicol can be taken during pregnancy. We need to dig into the “information for health professionals” to learn that, in animal trials, serious negative effects were observed:
reduction in fetal and placental weights, reduced fetal viability, increased limb and paw hyperflexion and abortions, were noted in the rabbit at a maternally toxic dose that was 3.3 x the maximum recommended dose in humans for treatment of chronic constipation and 1.3 x for faecal impaction. Rabbits are a sensitive animal test species to the effects of GI-acting substances and the studies were conducted under exaggerated conditions with high dose volumes administered, which are not clinically relevant.
The manifacturer of the drugs Movicol, Norgine Limited, and the UK medical bureaucrats who authorized the drug, wrote that the results in rabbits are not clinically relevant in humans. We think that ignoring the results on toxicity in animals is questionable. In general, it is recommended to explore natural ways to correct IBS-D (diarrhea) and IBS-C (constipation) before using drugs. If drugs are used, the available information on safety needs to be studied thoroughly.
Working Group on IBS-D, IBS-C and “functional constipation”.
We invite medical practitioners and people interested in optimizing their health to join our Working Group on IBS-D, IBS-C and “functional constipation”.
Selected references:
1. Spiller R. Irritable bowel syndrome: new insights into symptom mechanisms and advances in treatment. F1000Research 2016, 5(F1000 Faculty Rev):780.
2. Lam C, Chaddock G, Marciani L, et al.: Colonic response to laxative ingestion as assessed by MRI differs in constipated irritable bowel syndrome compared to functional constipation. Neurogastroenterol Motil. 2016.
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