Intestinal Ultrasound for Differentiating Fibrotic or Inflammatory Stenosis in Crohn's Disease: A Systematic Review and Meta-analysis

Background and Aims Intestinal ultrasound [IUS] has been increasingly reported to distinguish inflammatory or fibrotic intestinal stenosis in Crohn's disease [CD] patients. However, the diagnostic value is unclear. This systematic review and meta-analysis aimed to assess the diagnostic role of different modes of IUS parameters. Methods We searched PubMed, Embase, Web of Science, and Cochrane Library from inception to August 2021. Regarding effect sizes, weighted mean differences [WMDs] or standardised mean differences [SMDs] were used. We pooled data using a random-effects or fixed-effects model according to heterogeneity. The diagnostic accuracy of IUS for distinguishing fibrosis was pooled. Results A total of 19 studies were retained for qualitative analysis, and 14 were included in the meta-analysis [with 511 total subjects and 635 bowel segments]. In patients with fibrotic stenosis, the pooled WMDs for bowel wall thickness were 1.30 mm (95% confidence interval [CI]: 0.69-1.91) thicker than in patients with inflammatory stenosis, and the pooled SMDs for strain value and strain ratio were 0.80 [95% CI: 0.41-1.20] and 1.08 [95% CI: 0.55-1.60] harder than in patients with inflammatory stenosis, respectively. The percentage of maximal enhancement of fibrotic stenosis was lower than that of inflammatory stenosis [WMD -10.03; 95% CI: -17.91- -2.16]. The diagnostic accuracy of IUS was not performed because only a few studies provided relevant diagnostic indicators, and these studies used different modes and parameters. Conclusions IUS currently is inaccurate to differentiate fibrotic or inflammatory stenosis in CD patients, and more studies assessing the significance of each parameter and its cut-off value in different modes of IUS are needed to be conducted in the future.