New insights into the physiology of peritoneal fluid transport.

A review is given on the mechanisms of free water transport, the various methodologies for its measurement, its dependency on the osmotic gradient, and the assessment of osmotic conductance in individual patients. The importance of impaired free water transport in long-term ultrafiltration failure is discussed, relative to peritoneal solute transport status. Furthermore, the relationship of free water transport with locally released potassium is considered, together with a potential role of impaired K(+) channel function with peritoneal alterations. Finally, the role of impaired osmotic conductance to glucose and its effects on free water transport in long-term patients with ultrafiltration failure is reviewed.