Figure 5a. (a) Bar graph shows the effect of timing of postoperative US on minimum venous diameter. The bars are the mean plus or minus SD (P = .65), and the error bars are the SD. The measurements are not significantly different if obtained in the 2nd, 3rd, or 4th month after fistula construction, which suggests that measurements obtained at 4-8 weeks can be used to predict fistula outcome. (b) Bar graph shows the effect of timing of postoperative US on blood flow rate. The bars are the mean plus or minus SD (P = .78), and the error bars are the SD. The measurements are not significantly different if obtained in the 2nd, 3rd, or 4th month after fistula construction, which suggests that measurements obtained at 4-8 weeks can be used to predict fistula outcome.