O-011 YI Body Morphometric Changes on MRI After Initiation of Therapy in Children With Newly Diagnosed Small Bowel Crohn’s Disease

Abstract

Children with small bowel Crohn’s disease commonly present malnourished and then gain weight with the initiation of medical therapy. Little is known about body composition changes during this treatment period. The purpose of our study was to evaluate changes in body composition (subcutaneous adipose tissue and muscle) during the first 6 months of treatment. Children with newly diagnosed small bowel Crohn’s disease were prospectively recruited at a single center to undergo magnetic resonance (MR) enterography imaging at the time of diagnosis (T0), approximately 1 month (T1m) and approximately 6 months into treatment (T6m). Axial non-fat-saturated MR imaging at the level of the umbilicus was used to quantify subcutaneous adipose tissue and muscle cross-sectional areas (cm2) (Figure 1). Morphometric changes were correlated with changes in temporally-related laboratory values, short pediatric Crohn’s disease activity index (sPCDAI), and anthropometrics. Twenty-nine children (mean age 14.1 years; range, 9–17 years) participated in the study. 28 of 29 (97%) children received anti-TNFα therapy. Mean weight z-score and BMI z-score changes from T0 to T1m were 0.28 ± 0.07 and 0.48 ± 0.13 respectively (N = 25), and from T0 to T6m were 0.77 ± 0.08 and 0.77 ± 0.11 respectively (N = 19). Mean psoas muscle area change (T0 to T1m: 0.88 cm2 ± 0.21, N = 24; T0 to T6m: 1.94 cm2 ± 0.21, N = 19), mean subcutaneous adipose tissue area change (T0 to T1m: 13.96 cm2 ± 5.4, N = 24; T0 to T6m: 51.27 cm2 ± 11.05, N = 19). From T0 to T1m, increase in weight z-scores and BMI z-scores correlated with an increase in psoas area (r = 0.50, P = 0.013, and r = 0.43, P = 0.038 respectively; N = 24). From T0 to T6m, increase in weight z-scores and BMI z-scores correlated with an increase in psoas area (r = 0.55, P = 0.014 and r = 0.59, P = 0.0072; N = 19). There was no significant association between subcutaneous adipose tissue areas and weight z-scores (T0 to T1m: r = 0.39 P = 0.058, N = 24 and T0 to T6m: r = 0.22, P = 0.38, N = 19). There was a trend toward greater psoas area increase from T0 to T1m in younger patients (r = −0.27, P = 0.19, N = 24; Figure 2), while the change in subcutaneous adipose tissue area was more pronounced in older patients from T0 to T6m (r = 0.40, P = 0.091, N = 19; Figure 3). There was no difference in weight z-scores (P = 0.2), muscle area (P = 0.1), or subcutaneous adipose tissue area (P = 0.4) between boys and girls. There were no associations between change in sPCDAI, ESR or CRP with muscle area (P = 0.7, P = 0.2, P = 0.3) or with subcutaneous adipose tissue (P = 0.9, P = 0.2, P = 0.08). On average, children with newly diagnosed small bowel Crohn’s disease tend to gain significant muscle but not subcutaneous adipose tissue in the first 6 months after initiating medical therapy. Younger children may gain more muscle in the first month of treatment, while older children may gain more subcutaneous adipose tissue by 6 months of treatment. An initial increase in muscle mass may be a key contributor to weight gain and BMI increase in many pediatric patients treated for small bowel Crohn’s disease. Our findings are different from those described in adults receiving anti-TNFα therapy.