Is the peritoneal membrane durable indefinitely?

In general, the permeability characteristics of the peritoneal membrane are well maintained with time in the context of current technique survival rates. Some data would suggest that there is a tendency toward hyperpermeability in long-term PD patients; in a much smaller group of patients this may manifest itself as a loss in ultrafiltration capacity in the short term, that is within 2-4 years after CAPD initiation. A reduction in factors, which continue to have a significant negative effect upon technique survival, such as peritonitis and catheter-related infection will see patients remaining on the therapy for longer. This may place a sharper focus on ultrafiltration loss in the PD population, particularly that associated with increases in the permeability of the peritoneum. However, until such time as significant improvements occur it is likely the peritoneal membrane will continue to be more durable than the therapy in the vast majority of patients. It is now becoming clearer that the rate of decline of residual renal function (RRF) may be an important factor in the development of sequelae associated with inadequate dialysis. The role of RRF has often been overlooked when the clinical manifestations of inadequate UF and solute removal have become apparent and further study is required to determine the contribution of residual diuresis to the table of prognostic factors associated with long-term stability of the PD patient. Nevertheless, it is clearly an important parameter worthy of considerable future focus. Although membrane performance appears well maintained in general, routine monitoring of the mass transfer performance of the peritoneum should be performed. Assessment will facilitate focussed dialytic management and allow the clinician to recognise and pre-empt potential problems resulting from inadequate dialysis associated with decreasing or increasing membrane permeability in the small number of patients so affected: such monitoring should include measurement of the mass transfer coefficient at onset and every 6-12 months thereafter. However, the monitoring of RRF and overall solute clearance is perhaps of more significance in view of the contribution of RRF to overall dialytic prescription. The routine assessment of these parameters is also encouraged.