Body composition and outcomes in dialysis patients and renal transplant recipients

Overweight (body mass index [BMI] = 25 - 30 kg/m2) and obesity (BMI ≥ 30 kg/m2) have become mass phenomena with a pronounced upward trend in prevalence in most countries throughout the world and are associated with increased cardiovascular risk and poor survival. In patients with end stage renal disease (ESRD) undergoing maintenance hemodialysis an 'obesity paradox' has been consistently reported, i.e., a high BMI is incrementally associated with better survival. Whereas this 'reverse epidemiology' of obesity is relatively consistent in maintenance hemodialysis patients, studies in peritoneal dialysis patients have yielded mixed results. Moreover, the effect of pre- and post-transplant obesity in kidney transplanted patients on long-term graft and patient survival has not been well established. However, BMI is unable to differentiate between adiposity and muscle mass and may not be an acceptable metric to assess the body composition of ESRD patients. Assessing lean body mass, in particular skeletal muscle, and fat mass separately are needed in ESRD patients using gold standard techniques such as imaging techniques. Alternatively, inexpensive and routinely measured surrogate markers such as serum creatinine, waist and hip circumference or mid-arm muscle circumference can be used. We have reviewed and summarized salient recent data pertaining to body composition and clinical outcomes about the association of survival and body composition in maintenance dialysis patients and kidney transplanted recipients.