Preservation of residual renal function is of paramount importance because it is an independent risk factor of mortality in PD patients. In addition, achievement of adequate ultrafiltration is another crucial therapeutic goal to improve clinical outcomes in these patients. In this regard, if these two goals can be accomplished by icodextrin, it would be an ideal dialysis solution in PD practice. The investigators study will address this issue to answer the unresolved question on the effect of icodextrin on residual renal function."