Anthropometry and body composition in chronic kidney disease patients not on dialysis

Abstract

Chronic Kidney Disease (CKD), characterized by complex metabolic derangements is burdened by changes in nutritional status during the entire course of the disease. Overt malnutrition is usually observed in the late stages of CKD, but a decrease of body cell mass and other changes in body composition, for instance over-hydration, may occur early, even with no evidence of weight loss. The effects of alteration in nutritional status and body composition on clinical outcome are critical; protein-energy wasting by itself can worsen renal function and prognosis, being also strictly related to cardiovascular risk. On the other hand, some studies, but not all, have indicated that in CKD patients not yet on dialysis there is an inverse relationship between higher body mass index and some hard outcomes, such as mortality and cardiovascular events. In addition, body mass index seems to be a predictor of the onset of CKD in the general population; a possible association with waist circumference or waist-to-hip ratio has been described, as well. Thus, a challenge for nutritionists and nephrologists is to identify early changes of nutritional status in CKD patients in order to improve the patient's prognosis. International guidelines advise to assess nutritional status on a regular basis, but indications for CKD patients not yet on dialysis have been much less defined than those for dialysis patients. In addition, assessment of nutritional status in CKD requires multiple measurements and different techniques should be used concurrently. Anthropometry represents a first level assessment tool with some limitations because of the possible influence of an over-hydration state; although not very sensitive in detecting minor changes in body composition, it remains useful if associated with other nutritional tools. Among these, bioimpedance analysis (BIA) should be considered because it is very easy to perform at the bedside and can detect changes of body fluids in the early stages of CKD, such as blunted over-hydration in absence of clinically detectable edema. Thus, anthropometry and BIA should be used concurrently in the evaluation of nutritional status in CKD patients.