To this end, the Peritoneal Equilibration Test (PET), which is routinely performed in children during a day hospital treatment to analyse peritoneal transport function, will be modified. Instead of a single 4 hour standard dwell, two double mini PET using the same type and total volume of dialysate and the same total dwell time (150min) will be performed in randomised sequence in a total of 15 stable pediatric PD patients treated in four different European pediatric dialysis centres. The conventional double mini PET consists of two identical cycles (fill volume 1 L/m², 75 min), the adapted one of a short, small cycle (0.6 mL/m² BSA, 30 min) followed by a long, large cycle (1.4 mL/m², 120 min). A total of 22 ml of blood will be drawn via a peripheral i.v. line, intraperitoneal pressure, in clinical routine controlled once during a PET, will be measured with each dwell.