Residual kidney function in patients treated with maintenance dialysis has been recognized as an important metric for the past 3 decades, but is arguably still often overlooked. Multiple observational studies consistently show residual kidney function, as defined by small-solute clearance via the kidney, to be an independent risk factor for survival in both hemodialysis and peritoneal dialysis (PD) patients.1-4 Greater emphasis tends to be placed on residual kidney function in PD patients, given the observation that it declines more rapidly in those on hemodialysis therapy.