[How to evaluate body composition in chronic kidney disease?].

Onset of chronic kidney disease is rapidly followed by the occurrence of body composition alterations due to imbalance in sodium homeostasis and increased protein catabolism. These alterations lead to malnutrition and an increased cardiovascular risk and need to be accurately analysed. Numerous methods of body composition analysis are available but currently none is able to measure the five physiologic compartments -- extracellular fluid, intracellular fluid, body cell mass, bone mass and fat mass. Some are difficult to realize such the underwater weighing or neutron activation analysis, others are easier to do as skinfolds thickness or midarm muscle circumference measurements, dual energy X-ray absorptiometry (Dexa) or spectroscopic impedancemetry. These two techniques seem currently the most appropriate to measure fat mass, bone mass and lean mass for Dexa and body fluids for impedancemetry. The combination of Dexa and impedancemetry allows the calculation of body cell mass which is one of the most important parameter to evaluate nutritional status of patients with chronic kidney disease.