Background Preserving residual renal function (RRF) has always been the primary clinical goal for every nephrologists managing patients with chronic kidney disease but not yet on dialysis. RRF in patients on dialysis has proven to be a consistent and powerful predictor of mortality. This is particularly evident for patients treated with peritoneal dialysis (PD): CANUSA study showed that only RRF but not dialysis dose has significant predictive power of mortality [1].