A comparison of three methods to evaluate maximum bladder capacity: cystometry, uroflowmetry and a 24-h voiding diary in women with urinary incontinence

Background. Maximum bladder capacity (MBC) is an important parameter in the evaluation of lower urinary tract function. Yet, there is no consensus on how to measure MBC. The aim of this study was to compare estimates of the maximum bladder capacity (MBC) using cystometry, uroflowmetry, and a 24-h voiding diary in women with urinary incontinence. Methods. From 1 January 1998 to 31 December 1998 a retrospective review comprising 60 incontinent women in whom cystometry, uroflowmetry, and a 24-h voiding diary were performed were evaluated. Results. Median age was 55 years (range: 34-90 years). In women with detrusor instability (DI), MBC was significantly higher when measured using a voiding diary (median: 400 ml) as compared with cystometry (median: 215 ml) (p = 0.017). A 'Bland-Altman plot' demonstrated poor agreement between MBC in women with DI measured using a voiding diary and cystometry, respectively. The cystometric MBC was significantly higher in women with a stable detrusor (373 ml) as compared with women with DI (215 ml) (p = 0.0027). However, in women with or without DI there were no differences between MBC measured either using a voiding diary (400 vs. 360 mL) or by uroflowmetry (260 vs. 254 ml), respectively. Conclusions. A low cystometric MBC in women with DI may be an 'artefact' caused by the cystometric procedure (catherization and filling). The question is which measure of MBC is the best for clinical and scientific purposes.