Investigating sarcopenia in pediatric Crohn's Disease with magnetic resonance enterography: An observational study

Background and aims: Sarcopenia has a negative impact on clinical outcome in adult patients with Crohn's Disease (CD), but data on children are scarce. The aim of this study is to evaluate the prevalence of sarcopenia in children with CD using magnetic resonance enterography (MRE) and describe its relationship with baseline values and clinical outcome. Methods: We included children with a new diagnosis of CD from 2 tertiary referral pediatric Inflammatory Bowel Disease (IBD) centres, who underwent MRE at diagnosis between 2013 and 2023. Muscle mass was assessed by measuring the total area of the total psoas muscle (tPMA) at the level of the fourth and fifth lumbar vertebrae (L4/L5). Data were compared with pediatric reference values of tPMA, and sarcopenia was defined as a tPMA below the 3rd percentile. Demographic and anthropometric data, laboratory results, clinical disease activity and endoscopic index were collected at diagnosis and during follow-up. Clinical outcomes included relapse frequency, treatment changes, surgery, and IBD-related complications. Results: A total of 74 children (25 females, mean age 13.2 years) with CD were enrolled in the study. Sarcopenia was present in 34/74 patients (46 %) at diagnosis. Patients with sarcopenia had a lower Body Mass Index z-score and hemoglobin levels. Clinical disease activity (assessed using the Pediatric CD Activity Index) and endoscopic activity (assessed using the Simple Endoscopic Score for CD) were significantly higher in sarcopenic compared to non-sarcopenic children (median and quartiles scores: 25 [20, 40] vs. 21 [13, 35] and 10 [5, 13] vs. 6 [3, 13], respectively). During the follow-up period (median: 35 months; range: 1–99 months), no significant differences were observed between the sarcopenic and non-sarcopenic groups in terms of the composite outcome (defined as the occurrence of at least one unfavorable event). However, the rate of flares (number per person-year) was also higher in sarcopenic children compared to non-sarcopenic ones (27 % vs. 15 %; p = 0.0679). Conclusions: Sarcopenia is highly prevalent among children with CD at diagnosis. MRE-based muscle mass measurement correlates with traditional anthropometric measurements and can be valuable for comprehensive nutritional screening in pediatric CD patients. Patients with sarcopenia presented with more severe clinical, laboratory, and endoscopic findings at diagnosis; although sarcopenic children experienced more clinical relapses we were not able to show a significant association between sarcopenia and outcomes. Larger series need to be studied.