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P415. MRI assessment of body composition in paediatric Crohn's disease; intra-abdominal adipose tissue association with disease severity

D. Thangarajah1, K.E. Chappell2, C. Gale3, J.R. Parkinson1, J. Epstein4, W. Hyer4, K. Soondrum4, G. Frost5, J.M. Fell4, 1Imperial College, Section of Academic Neonatal Medicine, London, United Kingdom, 2Chelsea and Westminster NHS foundation trust, Radiology, London, United Kingdom, 3Imperial College, Section of Academic Neonatal medicine, London, United Kingdom, 4Chelsea and Westminster NHS foundation trust., Paediatric Gastroenterology department, London, United Kingdom, 5Imperial College, Nutrition and Dietetic Research Group, Faculty of Medicine, London, United Kingdom

Background

Paediatric Crohn's disease (CD) is associated with malnutrition, poor growth and alterations in body composition. Intra-abdominal adipose tissue (IAAT) is the adipose compartment most strongly associated with chronic inflammation; adipocytes can function as macrophage-like-cells in the inflammatory cascade, releasing adipokines such as IL-6, TNF-α. Intestinal adipose tissue expansion observed in surgical specimens is a recognised hallmark of CD.

Study aims: For the first time we use magnetic resonance imaging (MRI) as a method of measuring body composition in paediatric CD, specifically for quantifying intra-abdominal adipose tissue (IAAT).

Methods

Children (7–18 years) with CD were recruited from a tertiary Paediatric Gastroenterology department; healthy children were recruited to act as controls from general paediatric outpatients, Chelsea and Westminster hospital. Ethical approval was obtained. Volumes of the following abdominal compartments; Total abdominal adipose tissue (TAAT), IAAT, subcutaneous adipose tissue (SCA) and abdominal muscle (MU) were quantified from MR images for all subjects; volumes were expressed in litres.

Analysis: Compartment volumes were adjusted for body size by derivation of a height (Ht) index for each compartment (Compartment/(Ht)2); expressed as a ratio of TAAT:MU, and IAAT:SCA [1]. Measures were analysed according to disease activity; remission/mild (PCDAI [paediatric activity disease activity index] ≤29), moderate/severe (PCDAI ≥30). We have not fulfilled our recruitment target thus we present descriptive statistics.

Results

29 children were recruited; Mean age (±SD) (Controls (C): 14.4±1.9 yrs, n = 6 (4 boys); remission/mild (R/M): 14.2±2.2 yrs, n = 12 (6 boys); moderate/severe (M/S): 13.5±1.4 yrs, n = 11 (6 boys).

Mean BMI (C): 19.3±2.7 kg/m2; R/M: 19.6±4.3 kg/m2; M/S: 16.6±2.9 kg/m2.

The median [IQR] of TAAT:MU for each group; C: 0.61 [0.52–0.83]; R/M: 0.90 [0.60–1.50]; M/S: 1.26 [0.87–1.76].

For IAAT:SCA; C: 0.42 [0.27–0.54]; R/M: 0.37 [0.23–0.71]; M/S: 0.68 [0.36–1.20].

At the time of MRI scan no child was on systemic steroids. The plots in Figure 1 represent the median Compartment/(Ht)2 (bar); IQR (box) and range (error bars).

Figure 1: IAAT-Height Index and Muscle-Height Index.

Conclusion

Using MRI methodology we show that IAAT and related compartments can be quantified in children with CD. Our preliminary results indicate that severe disease is associated with lower muscle mass and higher IAAT. In severe disease despite lower BMI, there is evidence of higher IAAT; this implies that IAAT is mediated by local gastrointestinal inflammation.