Screening for muscle wasting and dysfunction in patients with chronic kidney disease.

Skeletal muscle mass and muscle function are negatively affected by a variety of conditions inherent to chronic kidney disease (CKD) and to dialysis treatment. Skeletal muscle mass and function serve as indicators of the nutritional and clinical state of CKD patients, and low values or derangements over time are strong predictors of poor patient outcomes. However, muscle size and function can be affected by different factors, may decline at different rates, and may have different patient implications. Therefore, operational definitions of frailty and sarcopenia have emerged to encompass these 2 dimensions of muscle health, i.e., size and functionality. The aim of this review is to appraise available methods for assessment of muscle mass and functionality, with an emphasis on their accuracy in the setting of CKD patients. We then discuss the selection of reference cutoffs for defining conditions of muscle wasting and dysfunction. Finally, we review definitions applied in studies addressing sarcopenia and frailty in CKD patients and discuss their applicability for diagnosis and monitoring.