Ultrafiltration failure in peritoneal dialysis: a pathophysiologic approach.

BACKGROUND: Ultrafiltration failure is a significant cause of technique failure for peritoneal dialysis and subsequent transfer to hemodialysis.
SUMMARY: Ultrafiltration failure is defined as failure to achieve at least 400 ml of net ultrafiltration during a 4 h dwell using 4.25% dextrose. Four major causes of ultrafiltration failure have been described. A highly effective peritoneal surface area is characterized by transition to a very rapid transport state with D/P creatinine >0.81. Low osmotic conductance to glucose is characterized by attenuation of sodium sieving and decreased peritoneal free water clearance to <26% of total ultrafiltration in the first hour of a dwell. Low effective peritoneal surface area manifests with decreases in the transport of both solute and water. A high total peritoneal fluid loss rate is the most difficult to diagnose clinically; failure to achieve ultrafiltration with an 8-10 h icodextrin dwell may provide a clue to diagnosis. KEY MESSAGES: Knowledge of the specific pathophysiology of the various causes of ultrafiltration failure will aid in the diagnosis thereof.