Quadriceps Muscle Layer Thickness in Kidney Transplant Recipients: A Potential Measure of Frailty and Sarcopenia

Introduction: Frailty and sarcopenia are related concepts that can impact outcomes after kidney transplantation. Measures of these two entities and new/emerging metrics of sarcopenia remain to be validated. Methods: In a prospective cohort study, kidney and kidney-pancreas transplant recipients were assessed at the time of transplant with the Physical Frailty Phenotype, bioimpedance analysis, quadriceps muscle layer thickness (QMLT), and CT. The impact on length of stay (LOS), prediction of frailty/sarcopenia, and relative concordance of metrics were analyzed. Results: Low QMLT, a putative surrogate of sarcopenia/frailty, was more frequently associated with longer LOS (\u3e14 days) after transplant. Additionally, QMLT was predictive of low muscle mass but insufficient at discriminating true sarcopenia, while CT of the abdominal muscles at the L3 level showed good discrimination for sarcopenia. Conclusions: Further exploration of QMLT and cut-offs for CT and functional metrics in the transplant population are required for future studies and risk stratification