Decompensated Bladder Following Bladder Outlet Obstruction 837 FIG. 1. Representative cystometrogram showing detrusor pressures and micturition volume in conscious sham rats (A), rats with bladder outlet obstruction (BOO) for 1 week (B), and rats with BOO for 2 weeks (C). The micturition interval significantly increased in rats with BOO for 2 weeks compared with those with BOO for 1 week. DP: detrusor pressure, VOL: volume. tions). Compliance was calculated according to the formula (P2-P1)/(V2-V1), where P2 represents the pressure of the stable curve just before the bladder contracts and V2 the infused volume at that time. P1 represents the baseline pressure and V1 the corresponding infused volume. 2) Parameters to investigate DO during the filling phase, in- cluding time of filling phase (interval between the ini- tiation of saline infusion and micturition), frequency of DO (per minute), and average pressure difference between the peak and the base of the DO (DO pressure). Statistical analysis. The results are given as mean val- ues±SEM. Normal distributions were confirmed by the Shapiro-Wilks’ W test. Statistical significance was de- termined with unpaired Student’s t-tests or a one-way ANOVA with the Tukey post-hoc test for multiple compari- sons. All analyses were performed with GraphPad Prism, version 5.03 (Graph Pad Software, San Diego, CA, USA). Statistical significance was considered at p＜0.05. RESULTS During the course of the experiment, 2 (20%) rats in the 1 week BOO group died, 1 (10%) rat in the 2 week BOO group died, and 1 (10%) rat in the sham group died. Representa- tive cystometric tracings from rats in the sham, 1 week BOO, and 2 week BOO groups are shown in Fig. 1. BOO was successfully produced in all surgically manipulated ani- mals. 1. Body and bladder weights There were no significant differences in body weight among any of the groups on the day of cystometry (data not shown). All of the groups with obstruction showed an increase in the ratio of bladder (mg) to body (g) weight compared with that in the sham group (p＜0.001). However, there were no significant differences in the ratio between the 1 week BOO and the 2 week BOO groups (p＞0.05) (Fig. 2A). 2. Urodynamic pressure- and volume-related parameters Compared with that in sham animals, basal pressure was elevated in both 1 week BOO (p＜0.05) and 2 week BOO (p ＜0.05) groups. There were no significant differences in the ratio between the 1 week BOO and 2 week BOO groups (p＞ 0.05). Compared with that in sham animals, threshold pressure was higher in the 2 week BOO group (p＜0.01) but not in the 1 week BOO group (p＞0.05). Neither BOO group showed any significant difference in maximal pressure compared with the sham group (p＞0.05) (Fig. 3). Compliance was decreased in the 1 week BOO group (p ＜0.01) and increased in the 2 week BOO group (p＜0.001) compared with the sham group (Fig. 2B). The 2 week BOO group showed increased compliance compared with the 1 week BOO group (p＜0.001) (Fig. 4). Compared with that in the sham group, the 1 week BOO (p＞0.05) group showed no significant difference in bladder capacity. This was due to increased residual volume (p＜0.05) and decreased mic- turition volume (p＜0.05) compared with that in the sham group. However, bladder capacity was increased in the 2 week BOO group (p＜0.01) compared with the sham group, which was associated with increased residual volume (p ＜0.01) and no difference in micturition volume (p＞0.05) in the 2 week BOO group compared with the sham group. The micturition interval was increased in the 2 week BOO group compared with the sham (p＜0.01) and 1 week BOO (p＜0.05) groups. According to the definition of decom- pensated bladder in our study, 62.5% of the 1 week BOO group (5 of 8 bladders) and 33.3% (3 of 9 bladders) of the 2 week BOO group showed decompensation. The 1 week BOO group showed 37.9% of residual volume, and the 2 week BOO group showed 27.6% on average. There was no significant difference between the two groups (Fig. 5). Korean J Urol 2011;52:835-841