Not only bowel: opportunistic assessment of sarcopenia in pediatric ulcerative colitis patients undergoing magnetic resonance enterography.

PURPOSE: Malnutrition and sarcopenia are under-recognized complications in pediatric inflammatory bowel disease, with an understudied interrelationship. This exploratory study aimed to estimate the prevalence of sarcopenia in children with newly diagnosed Ulcerative Colitis (UC) and to investigate associations between opportunistically MRE-derived muscle metrics and clinical, laboratory, and endoscopic disease activity.

MATERIALS AND

METHODS

Retrospective enrollment of 20 children aged 6-18 years who were ultimately diagnosed with UC and had undergone MRE as part of the systematic initial diagnostic work-up for suspected pediatric IBD. Total psoas muscle area (tPMA) was measured on axial T2-weighted images at the L3 vertebral level and used as a sarcopenia biomarker: "at risk of sarcopenia" with tPMA <10th percentile, and with "severe sarcopenia" ≤3rd percentile. Clinical activity was assessed using the Pediatric Ulcerative Colitis Activity Index (PUCAI), endoscopic severity using the Ulcerative Colitis Endoscopic Index of Severity (UCEIS), and laboratory markers including fecal calprotectin and inflammatory parameters. Group comparisons, correlation analyses, multiple linear regression were performed.

RESULTS

At risk of sarcopenia (tPMA <10th percentile) was observed in 65% of patients, while 30% met criteria for severe sarcopenia. Mild-to-moderate sarcopenia was not consistently associated with clinical or biochemical severity, while severe sarcopenia was associated with lower BMI (p = 0.001), higher PUCAI (p = 0.05), increased inflammatory markers (white blood cell count p = 0.04; neutrophils p = 0.03; CRP p = 0.003), and lower albumin levels (p = 0.001). In multiple regression analysis, PUCAI showed the strongest association with reduced muscle mass (p = 0.028).

CONCLUSION

In this small exploratory cohort, reduced muscle mass was observed at the time of UC diagnosis. MRE examinations acquired during the initial diagnostic work-up enabled opportunistic assessment of skeletal muscle mass. These preliminary findings are hypothesis-generating and require validation in larger, prospective, multicenter cohorts before any clinical risk-stratification role can be established.