PURPOSE: The diagnosis of bladder outlet obstruction in women by pressure flow study may be difficult because there are several definitions of bladder outlet obstruction, several parameters and no standard cutoffs. We evaluated the ability of pressure flow studies to separate women into unobstructed, equivocal and obstructed groups. MATERIALS AND METHODS: In a prospective study 85 women with lower urinary tract symptoms underwent clinical evaluation, including physical examination, voiding cystourethrography, endoscopy, flow rate and post-void residual volume measurement. A pressure flow study was performed 15 days later. The pressure flow study parameters were maximum flow, post-void residual volume, detrusor pressure at maximum flow, vesical pressure at maximum flow, area under the curve of detrusor pressure during voiding and area under the curve of detrusor pressure during voiding adjusted for voided volume. After considering the clinical evaluation 2 urologists classified the patients into 3 groups, namely unobstructed, equivocal and obstructed, as the traditional classification. Linear discriminant analysis was then performed using the traditional classification and pressure flow study data. RESULTS: Mean patient age was 55 years (range 18 to 83). According to the traditional classification there were 36 unobstructed, 28 equivocal and 21 obstructed cases. Significant differences were noted in all pressure flow study parameters (analysis of variance p <0.05). Linear discriminant analysis showed that area under the curve of detrusor pressure during voiding adjusted for voided volume was the most statistically discriminating parameter. Of the cases 86%, 36% and 57% were identically categorized by the traditional and area under the curve of detrusor pressure during voiding adjusted for voided volume parameter classifications in the unobstructed, equivocal and obstructed groups, respectively. The other pressure flow study parameters showed less satisfactory results. CONCLUSIONS: Area under the curve of detrusor pressure during voiding adjusted for voided volume appears to be the most discriminating urodynamic parameter of female bladder outlet obstruction. Other studies are needed to test the reliability and validity of this new parameter.
PURPOSE: The diagnosis of bladder outlet obstruction in women by pressure flow study may be difficult because there are several definitions of bladder outlet obstruction, several parameters and no standard cutoffs. We evaluated the ability of pressure flow studies to separate women into unobstructed, equivocal and obstructed groups. MATERIALS AND METHODS: In a prospective study 85 women with lower urinary tract symptoms underwent clinical evaluation, including physical examination, voiding cystourethrography, endoscopy, flow rate and post-void residual volume measurement. A pressure flow study was performed 15 days later. The pressure flow study parameters were maximum flow, post-void residual volume, detrusor pressure at maximum flow, vesical pressure at maximum flow, area under the curve of detrusor pressure during voiding and area under the curve of detrusor pressure during voiding adjusted for voided volume. After considering the clinical evaluation 2 urologists classified the patients into 3 groups, namely unobstructed, equivocal and obstructed, as the traditional classification. Linear discriminant analysis was then performed using the traditional classification and pressure flow study data. RESULTS: Mean patient age was 55 years (range 18 to 83). According to the traditional classification there were 36 unobstructed, 28 equivocal and 21 obstructed cases. Significant differences were noted in all pressure flow study parameters (analysis of variance p <0.05). Linear discriminant analysis showed that area under the curve of detrusor pressure during voiding adjusted for voided volume was the most statistically discriminating parameter. Of the cases 86%, 36% and 57% were identically categorized by the traditional and area under the curve of detrusor pressure during voiding adjusted for voided volume parameter classifications in the unobstructed, equivocal and obstructed groups, respectively. The other pressure flow study parameters showed less satisfactory results. CONCLUSIONS: Area under the curve of detrusor pressure during voiding adjusted for voided volume appears to be the most discriminating urodynamic parameter of female bladder outlet obstruction. Other studies are needed to test the reliability and validity of this new parameter.