Background Sarcopenia, the unintentional loss of skeletal muscle mass, is associated with poor outcomes in adult patient populations. In adults, sarcopenia is often ascertained by cross-sectional imaging of the psoas muscle area (PMA). Although children with chronic medical illnesses may be at increased risk for muscle loss because of nutritional deficiencies, physical deconditioning, endocrine anomalies, and systemic inflammation, consistent quantitative definitions for sarcopenia in children are lacking. We aimed to generate paediatric reference values for PMA at two intervertebral lumbar levels, L3-4 and L4-5. Methods In this cross-sectional study, we analysed abdominal computed tomography scans of consecutive children presenting to the emergency department. Participants were children 1-16 years who required abdominal cross-sectional imaging after paediatric trauma between January 1, 2005 and December 31, 2015 in a large Canadian quaternary care centre. Children with a documented chronic medical illness or an acute spinal trauma at presentation were excluded. Total PMA (tPMA) at levels L3-4 and L4-5 were measured in square millimetres (mm 2 ) as the sum of left and right PMA. Age-specific and sex-specific tPMA percentile curves were modelled using quantile regression. Results Computed tomography images from 779 children were included. Values of tPMA at L4-5 were significantly larger than at L3-4 at all ages, but their correlation was high for both girls (r = 0.95) and boys (r = 0.98). Amongst girls, tPMA 50th percentile values ranged from 365 to 2336 mm 2 at L3-4 and from 447 to 2704 mm 2 for L4-5. Amongst boys, 50th percentile values for tPMA ranged between 394 and 3050 mm 2 at L3-4 and from 498 to 3513 mm 2 at L4-5. Intraclass correlation coefficients were excellent at L3-4 (0.97, 95% CI 0.94 to 0.981) and L4-5 (0.99, 95% CI 0.986 to 0.995). Weight and tPMA were correlated, stratified by sex for boys (L3-4 r = 0.90; L4-5 r = 0.90) and for girls (L3-4 r = 0.87; L4-5 r = 0.87). An online application was subsequently developed to easily calculate age-specific and sex-specific z-scores and percentiles. Conclusions We provide novel paediatric age-specific and sex-specific growth curves for tPMA at intervertebral L3-4 and L4-5 levels for children between the ages of 1-16 years. Together with an online tool (https://ahrc-apps.shinyapps.io/sarcopenia/ ), these tPMA curves should serve as a reference enabling earlier identification and targeted intervention of sarcopenia in children with chronic medical conditions.

Sarcopenia predicts morbidity and mortality in adults with end-stage liver disease (ESLD) and is determined by total psoas muscle area (tPMA) measurement from computed tomography (CT) imaging. Recently developed pediatric age-and sex-specific tPMA growth curves provide the opportunity to ascertain the prevalence and impact of sarcopenia in children awaiting liver transplantation (LT). We performed a retrospective single-center study to evaluate sarcopenia in children with ESLD between 1 and 16 years of age with a clinically indicated abdominal CT less than 3 months before first isolated LT. Sarcopenia was defined as a tPMA z score less than −2 measured at the intervertebral L4-5 level. Patient demographic, biochemical, and outcome data were recorded. tPMA was compared to other measures of nutritional and growth status using univariate and multivariate logistic analyses. Outcome measures included 1-year morbidity events and mortality after LT. CT images from 25 (64% female) children with a median age of 5.50 (interquartile range [IQR], 3.75, 11.33) years were reviewed. Of the 25 children with ESLD, 10 (40%) had a tPMA z score less than −2. Sarcopenia was associated with lower z scores for weight (odds ratio [OR], 0.38; P = 0.02) and height (OR, 0.32; P = 0.03) and nutritional support before LT (OR, 12.93; P = 0.01). Patients with sarcopenia had a longer duration of pediatric intensive care unit (PICU) stay (3.50 [IQR, 3.00, 6.00] vs. 2.00 [IQR, 2.00, 3.50] days; P = 0.03). Sarcopenia was prevalent in 40% of children with ESLD who underwent clinically indicated CT while awaiting LT, and lower tPMA z score was associated with anthropometrics and need for nutritional support before LT. Post-LT PICU duration was increased in children with sarcopenia, reflecting adverse outcomes associated with muscle loss. Further studies are needed to elucidate the underlying mechanisms of sarcopenia in children with ESLD. Sarcopenia, defined as a decrease in skeletal muscle mass and function, is a frequent finding in adults with cirrhosis. (1-3) In a recent consensus statement by the North American Working Group on Sarcopenia in Liver Transplantation, computed tomography (CT) assessment of total psoas muscle area (tPMA) was recommended as the gold-standard technique to assess sarcopenia in patients with cirrhosis. (4) Unaffected by ascites, tPMA is linearly related to whole body mass, providing an estimation of overall lean muscle mass in patients with end-stage liver disease (ESLD).