Reliability and Validity of Mesenteric Fat Assessment by Intestinal Ultrasound in Pediatric Crohn’s Disease Using the Chicago Mesenteric Fat Index

BACKGROUND: Intestinal ultrasound (IUS) provides a noninvasive means of assessing Crohn's disease (CD), including visualization of mesenteric fat (MF) wrapping. Reliability of MF assessment and correlation with disease activity biomarkers in children is unknown. This study assessed the interrater reliability (IRR) of a binary assessment and a novel semi-quantitative index for grading MF wrapping using IUS (Chicago Mesenteric Fat Index [CMFI]) and correlation with disease activity biomarkers in pediatric patients with CD. METHODS: Children (≤18 years of age) with ileal CD who underwent IUS at 2 centers were enrolled. Three expert sonographers independently graded MF as present/absent and by the CMFI. IRR was calculated using Fleiss' kappa coefficient. Correlations between MF and clinical characteristics, inflammatory markers, and IUS data were calculated. RESULTS: Eighty IUS exams in 67 patients were included. The IRR was substantial for binary MF (κ = 0.744) and CMFI (κ = 0.618). Increasing CMFI grade was associated with bowel wall thickness (P < .001; odds ratio [OR], 16.35; 95% confidence interval [CI], 5.74-46.58), presence of ileal stricture (P < .001; OR, 30.32; 95% CI, 5.74-160.15), and presence of hyperemia (P = .001; OR, 6.59; 95% CI, 2.27-19.09). CONCLUSION: Assessment of MF on IUS is reproducible and reliable in pediatric CD. The CMFI can be used as a biomarker that mirrors biochemical and sonographic indicators of pediatric CD activity.