Magnetic resonance imaging of coeliac disease

Background Coeliac disease is an autoimmune disease affecting primarily the small bowel mucosa. Diagnosis is by blood test and duodenal biopsy, with the patient on a gluten-containing diet. The only treatment currently available is a gluten free diet (GFD). Further work is required to understand macroscopic gastrointestinal (GI) function and mechanisms of symptoms in coeliac disease. Magnetic Resonance Imaging (MRI) offers a unique tool to study GI fluid volumes, organ volumes and gut transit non-invasively. Objectives This study aimed to test the main hypotheses that: In adults newly diagnosed with coeliac disease, treatment with a GFD will reduce the water content of the fasting small bowel, the volume of the fasting colon and whole gut transit time (WGTT). This work also validated a new method for calibrating small bowel water content (SBWC) measurement on different MRI scanners. Methods 36 newly diagnosed patients and 36 healthy controls were recruited. They attended for an MRI visit having fasted overnight. SBWC, colonic volumes and WGTT were measured. Symptoms, expired breath hydrogen, stool diaries and stool samples were also collected. This was then repeated at 12 months follow-up. A validation study in healthy volunteers was carried out to calibrate and optimise the MRI scanner measurement of SBWC. Results No significant difference in SBWC was seen for the coeliac patients between baseline and 12 month follow up although there was significant difference in fluid volumes compared to the controls. Significant reductions were seen in the overall colonic volumes, and the ascending colon volumes in coeliac patients after treatment with a GFD. Ascending colon volumes and overall colonic volume were also larger in coeliac patients than in the controls both before and after treatment initiation with a GFD. A significant decrease in whole gut transit time was seen in coeliac patients between baseline and 12 month follow up. Transit time between coeliac patients and healthy controls was significantly slower both at baseline (44%) and at 12 month follow up (29%). Quality of life reported by the incident coeliacs was poorer than that in the healthy controls, even following GFD treatment. GI symptoms were significantly greater at baseline than at follow-up for the coeliac patients and although had improved following the GFD were still significantly higher than the controls at both time points. There was also a correlation seen between the severity of study day GI symptoms, and poorer PHQ_15 and overall HADS scores. Conclusion This study in patients with incident coeliac disease has shown for the first time that treatment with a gluten free diet for a year reduces the small bowel water, significantly reduces the overall colon volume and decreases the whole gut transit time. The coeliac patients also have greater SBWC than healthy controls at baseline and at follow up. Furthermore, the colon volumes are also larger at the time of diagnosis of coeliac disease and reduce over 12 month follow up on a gluten free diet. Finally, there is a significant reduction in whole gut transit time following a gluten free diet in the coeliac patients. The increased SBWC in coeliacs before and after treatment compared to healthy controls may represent an imbalance between absorption and secretion due to the damaged villi. These results support the underlying hypotheses of this work and show that MRI can be a useful non-invasive tool in evaluating coeliac patients and this work can add to our understanding of coeliac disease. This work provided also a new method to calibrate and standardise such small bowel water volume quantitation between scanners and laboratories