Biological basis of hypoalbuminemia in ESRD

Hypoalbuminemia is associated with mortality in patients with end-stage renal disease (ESRD) maintained either on peritoneal dialysis (PD) or hemodialysis (HD). Serum albumin concentration is determined by its rate of synthesis, by the catabolic rate constant (the fraction of the vascular pool catabolized per unit time), by external losses, and by redistribution from the vascular to the extravascular space. Hypoalbuminemia in dialysis patients is primarily a consequence of reduced albumin synthesis rate in both HD and PD patients, and in the case of PD patents, of transperitoneal albumin losses as well. Continuous ambulatory peritoneal dialysis patients are able to increase albumin synthesis to replace losses. Thus, ESRD does not directly suppress albumin synthesis. The rate of albumin synthesis is inversely proportional to the serum concentration of one potential acute phase protein (alpha2 macroglobulin), and albumin concentration is inversely proportional to that of either C-reactive protein or serum amyloid A in both HD and PD patients. The cause of decreased albumin synthesis is primarily a response to inflammation (the acute phase response), although it is possible that inadequate nutrition may also contribute. The cause of the inflammatory response is not immediately evident. There is no evidence that shifts of albumin to the extravascular space or that dilution of the plasma by volume expansion plays any role in causing hypoalbuminemia in ESRD patients.