Reliability of MR Enterography Features for Describing Fibrostenosing Crohn Disease

Abstract

Background Clinical decision making and drug development for fibrostenosing Crohn disease is constrained by a lack of imaging definitions, scoring conventions, and validated end points. Purpose To assess the reliability of MR enterography features to describe Crohn disease strictures and determine correlation with stricture severity. Materials and Methods A retrospective study of patients with symptomatic terminal ileal Crohn disease strictures who underwent MR enterography at tertiary care centers (Cleveland Clinic: September 2013 to November 2020; Mayo Clinic: February 2008 to March 2019) was conducted by using convenience sampling. In the development phase, blinded and trained radiologists independently evaluated 26 MR enterography features from baseline and follow-up examinations performed more than 6 months apart, with no bowel resection performed between examinations. Follow-up examinations closest to 12 months after baseline were selected. Reliability was assessed using the intraclass correlation coefficient (ICC). In the validation phase, after five features were redefined, reliability was re-estimated in an independent convenience sample using baseline examinations. Multivariable linear regression analysis identified features with at least moderate interrater reliability (ICC ≥0.41) that were independently associated with stricture severity. Results Ninety-nine (mean age, 40 years ± 14 [SD]; 50 male) patients were included in the development group and 51 (mean age, 45 years ± 16 [SD]; 35 female) patients were included in the validation group. In the development group, nine features had at least moderate interrater reliability. One additional feature demonstrated moderate reliability in the validation group. Stricture length (ICC = 0.85 [95% CI: 0.75, 0.91] and 0.91 [95% CI: 0.75, 0.96] in development and validation phase, respectively) and maximal associated small bowel dilation (ICC = 0.74 [95% CI: 0.63, 0.80] and 0.73 [95% CI: 0.58, 0.87] in development and validation group, respectively) had the highest interrater reliability. Stricture length, maximal stricture wall thickness, and maximal associated small bowel dilation were independently (regression coefficients, 0.09-3.97; P < .001) associated with stricture severity. Conclusion MR enterography definitions and scoring conventions for reliably assessing features of Crohn disease strictures were developed and validated, and feature correlation with stricture severity was determined. © RSNA, 2024 Supplemental material is available for this article. See also the article by Rieder and Ma et al in this issue. See also the editorial by Galgano and Summerlin in this issue.

Graphical abstract

Figure 1:

Flowchart of selection of the development group. The development phase included baseline and follow-up MR enterography examinations from 100 patients with Crohn disease who had symptomatic terminal ileal strictures. IPAA = ileal pouch-anal anastomosis, TI = terminal ileum. ¹Stricture was defined by the inclusion criteria (3-cm maximal associated small bowel dilation or the inability of a colonoscope to pass). ²As part of the consensus review process, 108 potential MR enterography examinations were re-reviewed by two senior radiologists at their respective institutions to ensure that there was no potential adhesive disease, prior strictureplasty, and/or image quality issues. If issues were identified by the respective central readers, the examination was excluded. Eight patients were ultimately excluded. ³Strictureplasty change proximal to neo-TI stricture interfered with measurement of proximal dilation (as detected by central readers and confirmed by senior radiologists not participating in the imaging interpretation). ⁴One patient was excluded during independent assessment (most distal stricture measured at baseline and follow-up was not the same stricture).

Figure 2:

Baseline MR enterography images in a 26-year-old male patient depict a long-segment naive stricture with marked inflammation and multiple areas of narrowing. Top row: Stricture length measurements made in the development phase by each central reader. The dotted lines indicate three-dimensional spline tool annotations, which are superimposed onto the two-dimensional image and correspond to the location of the stricture lumen on images that are outside of the imaging plane. Central readers created markings along the lumen of the stricture from the proximal to the distal end. Bottom row: Maximal associated small bowel dilation measurements made in the development phase by each central reader.

Figure 3:

Baseline MR enterography images in a 39-year-old female patient with a short naive stricture with inflammation involving the ileocecal valve and terminal ileum. Left, top and bottom: Coronal true fast imaging with steady-state precession images with fat saturation. Arrows point to a single stricture that was assessed by all four central readers. Top row: Variability in pulse sequences selected for length measurements and annotations from each of the four central readers in the development phase. Bottom row: Variability in pulse sequences selected for maximum small bowel dilation measurements and annotations from each of the four central readers. Stricture length, maximal associated small bowel dilation, and visual analog scale (VAS) evaluations made by each central reader are presented below the annotations. Stricture severity was rated with a VAS using a 100-mm continuous horizontal line that ranged from 0 (completely normal) to 100 (worst disease ever seen). Max = maximum.

Figure 4:

Central reader interpretations of four MR enterography features in the development phase using select images obtained in a 26-year-old male patient. (A) Coronal diffusion-weighted image. (B) Coronal fat-saturated postgadolinium image. (C) Coronal true fast imaging with steady-state precession and coronal single-shot fast spin-echo (inset) images. Arrows point to sacculation. (D) Coronal single-shot fast spin-echo image with fat saturation.

Figure 5:

Graphs of central reader measurements for (A) stricture length, (B) maximal associated small bowel dilation, (C) maximal stricture wall thickness, and (D) maximal luminal diameter for each patient in the development phase. Black dots indicate the mean measurement value for each patient. For each variable, patient values are displayed from the smallest to largest. The dotted horizontal line in A indicates a stricture length of 5.0 cm. The dotted horizontal line in B indicates maximum small bowel dilation of 3.0 cm. Note that measurement variability in maximal associated small bowel dilation remains relatively constant.

Figure 6:

Coronal single-shot fast spin-echo and postgadolinium images demonstrate the proximal, mid, and distal aspects of a naive stricture at MR enterography performed in a 71-year-old female patient. There is a long inflammatory stricture with multifocal areas of luminal narrowing and intervening areas of active inflammation involving the terminal ileum. The four central readers measured this stricture as being 70.1, 69.8, 71.7, and 71.6 cm in length. The visual analog scale estimate of the stricture severity was rated by the central readers as 65, 90, 80, and 75. The arrows point to a single stricture that was assessed by all readers. Colored dots in the left-most and right-most images are reader markings along the lumen of the stricture. Postgadolinium images are the middle images.