Magnetic resonance imaging of the gastrointestinal tract shows reduced small bowel motility and altered chyme in cystic fibrosis compared to controls

Cystic fibrosis (CF) is a genetic disease affecting mucosal secretions. Most patients experience digestive symptoms, but the mechanisms are incompletely understood. Here we explore causes and consequences of slower gastrointestinal transit using magnetic resonance imaging (MRI).Twelve people with CF and 12 healthy controls, matched for age and gender, underwent MRI scans both fasted and after standardised meals over a period of 6.5 hours. Images were assessed for small bowel motility, longitudinal relaxation time (T1) of ascending colon chyme, chyme texture and appearance of the colon wall.Small bowel motility scores were significantly lower in CF than in healthy controls in the fasting state (CF median 40 arbitrary units IQR [31, 46] vs Control 86 a.u. [52, 106], P=0.034). This difference was less pronounced postprandially. Furthermore, ascending colon chyme T1 was lower in CF than in controls (CF 0.59 s [0.38, 0.77] vs Control 0.79 s [0.55, 1.31], P=0.010). The difference in texture between small bowel and colon chyme, seen in health, was diminished in CF (difference in Haralick contrast 0.90 a.u. [0.38, 1.67] vs Control 2.11 a.u. [0.71, 3.30], P=0.010). Ascending colon mucosa in CF participants had an abnormal appearance compared to controls (Score 1-3, CF 2 [1, 3] vs Controls 1 [1, 1], P=0.019).Reduced small bowel motility and water content of ascending colon chyme are consistent with slower transit and constipation. MRI provides unique insights into chyme texture in the small bowel (suggesting bacterial overgrowth) and the appearance of the colon mucosa (suggesting altered mucus) in CF.Key point summary-People with cystic fibrosis (CF) have intrusive digestive symptoms and severe gut complications, but mechanisms are incompletely understood.-In this study, 12 people with CF were compared to healthy controls, undergoing repeated MRI scans before and after standardised meals.-Fasted small bowel motility is reduced in people with CF, consistent with slower transit. In addition, a reduced colonic chyme water content and abnormal appearance of small bowel and colonic chyme as well as colonic mucosa suggest small bowel bacterial overgrowth, fat malabsorption and abnormal mucus production-These MRI outcomes hold promise in the assessment of therapeutic interventions.