The difference in causes of early and late ultrafiltration failure in peritoneal dialysis

Ultrafiltration failure (UFF) is a major complication of peritoneal dialysis. Although it seems associated with long-term treatment, it can also occur in recently started patients. To identify the causes of this complication in patients with early and late UFF we studied a group of 48 patients. Patients were classified as early if they had been treated for less than 2 years and as late if they had been treated for more than 4 years.

The patients were studied using a standard peritoneal permeability analysis. They all had a net ultrafiltration of less than 400 mL after a 4-hour dwell with 3.86% glucose. As possible causes for UFF, the solute transport parameters dialysate-to-plasma ratio (D/P) and mass transfer area coefficient of creatinine were compared, as well as the effective lymphatic absorption rate (ELAR) and the maximum dip in D/P sodium as an assessment of osmotic conductance to glucose.

25 short-term patients were compared with 23 long-term patients. Both groups showed an equal distribution of high small solute transport rates as a cause of UFF. The chi-square test showed that a high ELAR was a more frequent cause in early UFF compared to late UFF. However, a decreased osmotic conductance to glucose was significantly more often observed in late UFF. Some patients showed more than one cause of the complication.

This study has shown that UFF in long-term patients is often caused by a decreased osmotic conductance to glucose, most likely caused by a dysfunction of peritoneal water channels in combination with increased peritoneal surface area. In short-term patients, aquaporin dysfunction is rare, but a high ELAR was a very important factor in the occurrence of UFF.