Urodynamic parameters for the diagnosis of bladder outlet obstruction in women

Bladder outlet obstruction (BOO) is often overlooked in the diagnosis of women with lower urinary tract symptoms. Although the incidence of BOO is not high in the female population with lower urinary tract symptoms, a correct diagnosis for BOO is important. This study was designed to compare the urodynamic parameters in women with bladder outlet obstruction (BOO), stress urinary incontinence (SUI) and asymptomatic volunteers.

Videourodynamic study was performed in 76 patients who were clinically diagnosed as BOO, 265 with stress urinary incontinence (SUI). In addition, 30 asymptomatic female volunteers were recruited and served as controls. Voiding pressure (P(det.Qmax)), maximum flow rate (Qmax), and urodynamic parameters were compared among the BOO, SUI and control groups and the criteria values for BOO in women were estimated.

BOO was identified in 30 women with bladder outlet stricture, 40 women with dysfunctional voiding, and 6 women with high-grade cystocele. The mean P(det.Qmax) was significantly higher and the mean Qmax was significantly lower in the obstructed groups. When a P(det.Qmax) > or =35 cm H(2)O was set as the criteria for BOO, the sensitivity was 96.1% and specificity was 89.0%, whereas a P(det.Qmax) of > or =30 cm H(2)O had a sensitivity of 100% but the specificity was only 65.5%. If the criteria of BOO was set as P(det.Qmax) > or =35 cm H(2)O combined with Qmax < or =15 ml/s, the sensitivity for BOO was 81.6% and specificity was 93.9%.

Our results demonstrate a P(det.Qmax) of > or =30 cm H(2)O is a good index value for screening of female BOO. When a P(det.Qmax) of > or =35 cm H(2)O combined with a Qmax < or =15 ml/s was found, a high suspicion of BOO should be raised, for which a specificity of 93.9% and sensitivity of 81.6% for BOO was obtained.