Investigation and management of ultrafiltration failure in CAPD

Apparent loss of peritoneal ultrafiltration capacity may occur when fluid intake is excessive, residual urine volumes decrease or the patient does not perform exchanges regularly and should be suspected if drain volumes are unchanged. True loss of ultrafiltration capacity (reduced drain volumes) is potentially reversible if due to catheter malposition, internal dialysate leakage or recent peritonitis but is usually permanent if kinetic studies indicate a sustained reduction in net transcapillary ultrafiltration or increased lymphatic drainage. Three types of irreversible ultrafiltration failure have been identified of which high peritoneal solute transport rates resulting in rapid dialysate glucose absorption (Type 1 membrane failure) is the most common. Transcapillary ultrafiltration may also be reduced due to very low peritoneal solute transport rates (Type 2 membrane failure) in patients with sclerosing peritonitis or massive peritoneal adhesions but is now rare. Ultrafiltration failure due to high lymphatic drainage (Type 3 failure) is also uncommon. Treatment strategies in patients with Type 1 failure include achieving the maximum urine output with diuretics, reducing fluid intake to the minimum tolerated by the patient, changing to short dwell exchanges (daytime ambulatory peritoneal dialysis (DAPD) or machine peritoneal dialysis overnight) and temporary hemodialysis which may lead to a spontaneous reduction in peritoneal transport rates in some patients. Patients with Type 2 and Type 3 failure require permanent transfer to hemodialysis.