Simultaneous measurement of peritoneal glucose and free water osmotic conductances.

Ultrafiltration (UF) failure is one of the most important causes of long-term peritoneal dialysis (PD) failure in patients. Osmotic forces acting across small and ultra-small pores generate a UF with solutes through the small pore and free water transport (FWT) through the ultra-small pore. The ability of glucose to exert an osmotic pressure sufficient to cause UF is the so-called 'osmotic conductance to glucose' (OCG) of the peritoneal membrane. Our study proposes a simple method to determine both the OCG and FWT. In 50 patients on PD, a Double Mini-Peritoneal Equilibration Test (Double Mini-PET), consisting of two Mini-PET, was performed consecutively. A solution of 1.36% glucose was used for the first test, whereas a solution of 3.86% glucose was used for the second test. The sodium removal values and the differences in UF between the two tests were used to calculate FWT and the OCG. Patients with UF failure showed significant reductions not only in the OCG and the FWT but also of UF of small pores. The Double Mini-PET is simple, fast, and could become useful to evaluate patients on PD in everyday clinical practice.