Refining diagnosis of anatomic female bladder outlet obstruction: Comparison of pressure-flow study parameters in clinically obstructed women with those of normal controls

To improve the definition of pressure-flow study cutoff values for anatomic female bladder outlet obstruction (BOO) by comparing these parameters in women with clinical obstruction with those of normal controls. In the past 3 years, 82 consecutive women with clinical anatomic BOO were investigated according to an institutional review board-approved protocol that included imaging and urodynamic studies. The data from these women were then added to those of our previously published cohort of 87 patients. The controls were 20 female volunteers without any urologic complaints and without a history of bladder or urethral surgery who had undergone a urodynamic study. Three groups of women with BOO were identified in the most recent cohort: 20 with Stage III-IV cystocele, 23 who had undergone previous anti-incontinence surgery, and 39 with distal periurethral fibrosis or stricture. The optimal combination of the maximal flow rate (Qmax) and detrusor pressure at maximal flow rate (PdetQmax) for determining BOO was calculated using nonparametric receiver operating characteristic curves for the entire cohort of 169 women with obstruction. Age, Qmax, and PdetQmax were similar among the three BOO groups. The area under the receiver operating characteristic curve for BOO was 0.762 for Qmax (95% confidence interval 0.661 to 0.864, P <0.001) and 0.721 for PdetQmax (95% confidence interval 0.617 to 0.824, P <0.001). After adjusting for the effect of age, PdetQmax (P <0.001) and Qmax (P <0.011) were independently associated with BOO. After adjusting for age and using normal controls rather than an incontinent control population, we present pressure-flow study cutoff values to aid in the urodynamic study diagnosis of women with anatomic BOO.