Quest for V: body composition could determine dialysis dose.

Since the demonstration that dialysis patients with lower body weight have a higher mortality than larger patients, there has been much interest in determining possible mechanisms and any possible relationships to the dialysis dose. Arguments have been made against using Kt/V(urea) as the basis for dialysis prescription. Efforts have been made to determine a parameter of dialysis delivery independent of body size. An emerging area of intense research interest has explored the body composition determinants of resting metabolic rate. Based on the knowledge of in vitro organ tissue energy production, newer high-resolution imaging methods have been applied as a means of establishing the sources of resting energy production in chronic kidney disease (CKD) patients. However, the linkages between resting energy expenditure (REE), body composition, and survival have not received much attention despite various studies exploring the effect of renal dysfunction and of the hemodialysis process on REE. We explore possible mechanisms leading to a higher mortality in smaller (lower body mass index) patients. The hypothesis of Morton and Singer is discussed. We have hypothesized that delivery of dialysis based on visceral organ volume (V(organ)), which could be the appropriate representation of uremic toxin generation, would be more logical than the current practice. This retains the concept of Kt/V but suggests that instead of the total V, a component related to major metabolic activity might represent the volume of interest. As per our hypothesis, smaller dialysis patients would need relatively a higher dialysis dose delivery, as expressed by current Kt/V, in order to achieve the same level of clearance of uremic toxins as in larger patients.