*Purpose: Sarcopenia, or decreased muscle mass and function, is prevalent in adults with end-stage liver disease and negatively affects outcomes in liver transplantation (LT). Sarcopenia, and its impact on post-transplant outcomes, in children who require LT is poorly understood. We hypothesized that children who required LT would have significantly lower muscle mass than controls as measured by the psoas muscle surface area (PMSA) and that lower PMSA would be associated with poorer LT outcomes.

*Methods: Demographic and transplant-specific data were collected on all children listed for LT at our center between March 2009 and August 2018. Children who required liver-kidney or a 2^nd LT were excluded. PMSA at the 4^th lumbar vertebrae (L4) was measured on abdominal CT or MRI and compared to the PMSA of age- and gender-matched controls. In patients who underwent LT, the impact of muscle wasting on transplant-associated outcomes was assessed by linear regression and survival analysis.

*Results: We studied 67 subjects (mean age 5.6 years ± 5.9 years, 49% male) with chronic liver disease (49% biliary atresia) listed for LT. Of these, 59 patients underwent LT. There were 4 deaths on the waitlist and 4 patients removed from the list. They were compared to 63 healthy controls (mean age 5.8 years ± 6.0 years, 52% male). PMSA was significantly lower in children listed for LT than in controls: 709.35 ± 597.18 mm² in LT candidates vs. 1032.66 ± 902.66 mm² in controls, p=0.02. PMSA correlated significantly with weight (R= 0.87, p <0.001), mid-arm circumference (R= 0.77, p<0.001), and triceps skin folds (R=0.58, p<0.001). LT candidates had a mean wait time of 4.5 ± 5.9 months. At the time of transplant, mean calculated PELD/MELD score was 14.5 ± 10.0 with a mean appealed score of 27.3 ± 7.8. They spent a mean 1.7 ± 5.3 days intubated, 8.6 ± 13.8 days in the ICU and 18.9 ± 18.8 days in the hospital. Lower PMSA correlated significantly with longer intubation (R= -0.38, p 0.003), ICU length of stay (LOS) (R= -0.54, p <0.001), and total hospital LOS (R= -0.4, p 0.002) following transplant. Survival analysis using Cox proportional hazards, adjusted for age, showed an increase risk of death with lower PMSA (HR 0.994, p=0.005).

*Conclusions: Children listed for LT were significantly more sarcopenic (evidenced by a lower PMSA) than healthy age-matched controls. Commonly accepted indicators of nutritional status such as skin fold measurements did correlate with measures of sarcopenia; however, PMSA may provide a more robust functional marker of overall health. Pediatric LT candidates with lower PMSA had more complicated post-transplant courses and were more likely to die. Prospective studies are needed to determine the best means of assessing sarcopenia and understanding mechanisms of muscle wasting in children with chronic liver disease.

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