Also, the level of blood urea was higher than normal in both group with lower value in the HF group compared with the LF group (pre-dialysis: 21.77 ± 6.67 mmol / L vs 26.54 ± 7.64 mmol / L, P < 0.05, and post-dialysis: 7.06 ± 2.54 mmol / L vs 9.41 ± 3.26 mmol / L, P < 0.01, respectively).