Bladder capacity in patients with detrusor overactivity (DO) is known as reduced bladder volume commonly, it is essential that we evaluate bladder capacity in investigating the problem of urinary urgency and urinary incontinence. Urodynamic reserve bladder capacity (RC = maximum desire to void, MDV - normal desire to void, NDV) is a newly defined category. In our urodynamic laboratory, RC seems to relate with urinary urgency and urge urinary incontinence in real life. However, little data concerning RC is available thus far. Therefore, we present our RC data and the results of analysis of patients with DO and those without DO in terms of RC.

Sixty patients were recruited who underwent urodynamic study (UDS) for their lower urinary tract symptom. Among them, 30 patients had DO: 10 patients had phasic DO, 20 patients had terminal DO (12 men, 18 women, mean age 76.8 ± 58.5 years); 30 patients had no DO (17 men, 13 women, mean age 79.4 ± 49.2 years). There was no difference between DO and no DO groups in terms of sex and age.  We described RC in each group as MDV - NDV during filling phase in UDS. Also, we described a difference between first sensation, FS and MDV. We interviewed their bladder sensation following ICS terminology, in terms of NDV we obtained NDV as the feeling that each patient go to the restroom and void in everyday life in addition to ICS's definition (The feeling that leads the individual to void at the next convenient moment, but voiding can be delayed if necessary). Phasic DO and terminal DO were  based on observation of urodynamic wave form according to ICS report (2002). Cystometory was performed with double lumen catheter 6Fr at a filling rate of 50 mL/min using a Solar ®　from MMS. Mann- Whitney test were used determine significance between patients with DO and without DO.

Urodynamic FS was felt 13 patients without DO (150.4 ± 67.0mL) and 12 patients with DO (126.8 ± 117mL); 2 patients with phasic DO, 10 patients with terminal DO. Urodynamic NDV was 227.4 ± 144.2mL in patients without DO and 215.6 ± 116.5mL in patients with DO (not statistically significant); 165.5 ± 72.9 ml in phasic DO, 240.7 ± 127.4 ml in terminal DO (not statistically significant). Urodynamic RC was 230.0 ± 80.1mL in patients without DO, 151.6 ± 88.1mL in patient with DO (statistically significant, p<0.05); 126 ± 41.9mL with phasic DO, 66.2 ± 63.4mL with terminal DO. In patients with DO, the urodynamic RC in patients with ND at DO occurring was smaller than with ND before DO occurring, especially with terminal DO.

In our study, the urodynamic RC in patients with DO was smaller than without DO, while urodynamic NDV was no different between DO and no DO group significantly. The urodynamic RC had the tendency to decrease in patients with DO against without DO. In DO patients, urodynamic RC was subject to small in patients with ND at DO occurring to ND before DO occurring, especially terminal DO.

We presented RC data and the results of analysis of patients with DO and those without DO in terms of RC n ewly. This study showed that the urodynamic RC (MDV - NDV) in patients with DO was smaller than without DO. In DO patients, urodynamic RC was subject to small in patients with ND at DO occurring to ND before DO occurring, especially terminal DO. It might be estimate reserve bladder capacity in everyday life in individuals and reflect urinary urgency and urge urinary incontinence in real life. Taking NDV during filling phase in UDS and using RC may be beneficial to observe DO more deeply and evaluate storage function in more detailed.