Viscoelastic properties of small bowel mesentery at MR elastography in Crohn’s disease: a prospective cross-sectional exploratory study

Background: Creeping fat is a pathological feature of small bowel Crohn’s disease (CD), with literature suggesting that bowel resection with extended mesenteric resection is related to less postoperative recurrences. Conventional imaging is unable to accurately quantify the disease involvement (i.e., fibrosis) of creeping fat. Quantification of disease involvement could be useful in decision-making for additional extended mesenteric resection. We investigated the feasibility of magnetic resonance elastography (MRE) of the mesentery and if MRE is capable to detect fibrotic disease involvement of mesentery in active CD. Methods: Multifrequency MRE yielded spatial stiffness (shear wave speed, SWS, |G*|) and fluidity maps (φ). Viscoelastic properties of seven CD patients’ mesentery were compared to age- and sex-matched healthy volunteers (HV) (Mann–Whitney U-test). Within CD patients, the affected and “presumably” unaffected mesentery were compared (Wilcoxon-signed rank test). Repeatability was tested in 15 HVs (Bland–Altman analysis, coefficient of variation [CoV]). Spearman rank correlations were used to investigate the relation between microscopically scored amount of mesenteric fibrosis and viscoelastic parameters. Results: SWS, |G*|, and φ of affected mesentery in CD were higher compared to HV (p = 0.017, p = 0.001, p = 0.017). Strong correlations were found between percentage of area of mesenteric fibrosis and SWS and |G*| (p < 0.010). No differences were found within CD between affected and presumably unaffected mesentery. Repeatability of SWS showed 95% limits of agreement of (-0.09, 0.13 m/s) and within-subject CoV of 5.3%. Conclusion: MRE may have the potential to measure fibrotic disease involvement of the mesentery in CD, possibly guiding clinical decision-making with respect to extended mesenteric resection. Trial registration: Dutch trial register, NL9105 , registered 7 December 2020. Relevance statement: MRE may have the potential to measure the amount of mesenteric fibrosis of the affected mesenteric fat in active Crohn’s disease, giving more insight into disease progression and could potentially play a role in clinical decision-making for extended mesenteric resection. Key points: • MRE of the mesentery in patients with active CD is feasible. • Fluidity and stiffness of the mesentery increase in active CD, while stiffness correlates with the histopathological amount of mesenteric fibrosis. • MRE provides biomarkers to quantify mesenteric disease activity in active CD. Graphical Abstract: [Figure not available: see fulltext.]