P0693 The Chicago Mesenteric Fat Index: A Novel Biomarker for Assessing Inflammation in Pediatric Crohn’s Disease with Point of Care Intestinal Ultrasound

Abstract Background Pediatric Crohn’s disease (CD) is a chronic, progressive disorder that may result in lifelong disability. There is a need for tools that facilitate early detection and accurate assessment of disease. Point-of-care intestinal ultrasound (IUS) is an accurate and non-invasive tool that provides an alternative to magnetic resonance and/or computed tomographic enterography. In addition to bowel wall thickness (BWT) and hyperemia, mesenteric fat (MF) is one of the measures of CD severity visualized with IUS. Current guidance for grading MF is subjective and binary. We have previously proposed the Chicago Mesenteric Fat Index (CMFI) to standardize grading MF in adults, and demonstrated moderate to substantial inter-rater reliability (IRR). The aim of this study was to determine the IRR of MF assessment and validate the CMFI in pediatric CD. Methods IUS images of children with ileal CD were captured from November 2023 to May 2024. Those with prior surgery were excluded. CMFI differentiates severity based on the degree of wrapping: "none" (none or minimal MF wrapping), "incomplete" (incomplete circumferential MF wrapping with skipped areas along the terminal ileum), and "complete" (circumferential MF wrapping, continuous along the terminal ileum) (Figure 1). MF grading was performed by experienced pediatric intestinal sonographers, blinded to clinical data. IRR was analyzed using Cohen’s kappa statistic. We used population and clinical data and assessed the correlation of MF using chi-square for categorical data and Kruskal-Wallis for continuous variables. Results 48 IUS examinations in 36 patients were included [50% female, 69% ileocolonic disease, predominately non-stricturing, non-penetrating in 67%]. Median BWT on IUS was 3.55 mm [1.9-5.25] (Table 1). Of the 48 scans, 32 (67%) had presence of MF wrapping,16 had incomplete MF wrapping and 16 had complete MF wrapping. The IRR for the binary assessment of MF was substantial (k = 0.6936), and grading according to the CMFI also showed substantial agreement (k = 0.6038). MF was associated with other IUS parameters, including BWT (p<0.001 for both binary and graded index and binary), loss of bowel wall stratification (p = 0.001 for binary assessment and p = 0.002 for graded index) and the presence of hyperemia (p = 0.002 for binary assessment and p = 0.011 for graded index). MF was not associated with ileal strictures (p = 0.224 for graded index, p = 0.132 for binary assessment) (Table 1). Conclusion We demonstrate that IUS is a reliable tool for the assessment of MF in pediatric CD. MF assessment with the CMFI could be used as a potential objective non-invasive biomarker of CD severity in children, allowing for enhanced clinical decision-making and improved outcomes.

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