Results Prior to the study, urine volume (UV) in H-group was higher (P = 0.034), but pertinent data including TKV and kidney function slopes were not significantly different between two groups. During the study, UV further increased (P <0.001) in H-group but not in F-group. Plasma copeptin was lower (P = 0.024) in H-group than in F-group. Kidney function and TKV slopes became worse in H-group (P = 0.011 and 0.047, respectively) but not in F-group. High UV associated with increased urine sodium (UNa) and rapid decrease in eGFR(Eqcr-cys) (MDRD equation with cystatin C incorporated) (P = 0.043). UNa positively correlated with % increase in TKV (P = 0.014) and plasma copeptin weakly with increase in TKV (P = 0.038), respectively.