Risk of extracellular volume expansion in long-term peritoneal dialysis

Although direct evidence is unavailable, indirect evidence strongly suggests that the risk of extracellular (EC) volume expansion increases with long-term peritoneal dialysis (PD). Long-term PD patients routinely develop loss of residual renal function (RRF) and often develop increased rates of peritoneal solute transport. Loss of RRF is associated with hypervolemia and increased risk of death. It is also indirectly linked both to development of high peritoneal transport (through the prescription of larger hypertonic dextrose loads) and to further limitations of peritoneal sodium removal [through automated PD (APD), which is often prescribed as a means of increasing peritoneal clearances as renal clearances decrease, and which causes, through its shortened dwell periods, low rates of peritoneal sodium removal]. High peritoneal solute transport limits peritoneal ultrafiltration and sodium removal; it is a recognized risk factor for hypervolemia. Many cross-sectional studies measuring EC volume have documented moderate to severe hypervolemia in large numbers of PD patients. In long-term PD, hypervolemia has severe consequences including morbidity and mortality. Preventing hypervolemia in PD patients requires a focus on maintaining sodium balance. The means include lowering the dialysate sodium concentration for APD exchanges, using icodextrin, and, primarily, reducing dietary sodium intake to a level determined by monitoring the patient's sodium removal rate in urine plus dialysate. Periodic measurements of sodium removal rates and appropriate adjustments of dietary sodium intake should be considered measures of adequacy in PD.