Rates of solute diffusion in peritoneal dialysis

Dialysate-to-plasma concentration ratios (with 1.0 reflecting complete equilibration) for urea, creatinine, inulin, and protein during an eight-hour period in which dialysate is allowed to dwell in the peritoneum. Urea equilibration is so rapid that diffusion begins to level off at 90 to 120 minutes, and is essentially complete at 240 minutes. Thus, short dwell times will maximize the rate of urea removal. In comparison, larger molecules show a progressive decline in the rate of diffusion. Inulin diffusion, for example, increases linearly with time since a limiting concentration gradient is not approached. As a result, increasing the total time of dialysis enhances the rate of clearance of these larger molecules.