 Peritoneal dialysis PD is one of established treatments in the end stage renal disease patients. Volume overload is a predictor of mortality in PD patients. In this Randomized controlled trial, the investigators use the Body Composition Monitor BCM, a multifrequency bioimpedance device, to measure the level of overhydration in PD patients and explore its value in fluid management in peritoneal dialysis patients as well as their prognosis. 