The Chicago Mesenteric Fat Index: A Novel Metric for Point-of-Care Intestinal Ultrasound Evaluation of Mesenteric Fat Wrapping in Crohn's Disease.

BACKGROUND

Mesenteric fat (MF) wrapping is a characteristic feature of Crohn's disease (CD). Current assessment methods are limited to binary classification (presence/absence), restricting their utility in assessing disease progression and treatment response. This study aimed to develop and validate a novel semi-quantitative metric for grading MF wrapping using intestinal ultrasound (IUS), and to evaluate its reliability and clinical relevance.

METHODS

This cross-sectional study included 95 ultrasound scans from 63 patients with CD. The novel index described here categorized MF wrapping into 3 categories: none, incomplete, and complete. Images were independently assessed to evaluate inter- and intrarater reliability. Associations between MF wrapping and clinical characteristics, inflammatory markers, and IUS parameters were analyzed.

RESULTS

Interrater reliability for the MF index was moderate (κ = 0.452), while intrarater reliability was substantial (κ = 0.653), similar to binary assessment (κ = 0.572 and κ = 0.674 for inter- and intrarater reliability, respectively). MF wrapping was significantly associated with increased bowel wall thickness (OR, 6.74; P < .001), loss of bowel wall stratification (OR, 22.05; P < .001), hyperemia (OR, 8.09; P = .002), and presence of strictures (OR, 4.30; P = .002). Smoking status and lower serum albumin were significantly associated with increased MF wrapping.

CONCLUSIONS

CMFI represents a proof-of-concept tool for semi-quantitative assessment of MF wrapping on IUS. While reproducible and associated with other disease markers, its incremental clinical utility remains to be established through prospective validation and longitudinal outcome studies.