Proposed cutoff values to define bladder outlet obstruction in women

There is no accepted urodynamic definition of outlet obstruction in women. Currently, the diagnosis is made on the basis of history and radiographic and endoscopic findings. The goal of this study is to design a pressure-flow nomogram (PdetQmax/Qmax) and define cut-off values for obstruction.

Two groups were studied prospectively in an open study: 124 control and 35 clinically obstructed patients. All had a complete history, physical examination, normal neurologic evaluation, cystoscopy, voiding cystography, and urodynamics-with-pressure-flow study. Pressure-flow plot and receiver operator characteristic curves (ROCs) were constructed to determine optimal cut-off values to predict obstruction for peak flow rate (Qmax) and detrusor pressure at maximal flow (PdetQmax).

The etiology of obstruction was previous anti-incontinence surgery (n = 13), large cystocele (n = 11), urethral stricture (n = 6), and other (n = 5). On the basis of ROC curves, using cut-off values of Qmax of 15 mL/s or less and 12 mL/s or less, sensitivity was 85.7% and 71.4%, and specificity 78.2% and 90.3%, respectively. Using cut-off values of PdetQmax of more than 25 and more than 30 cm H2O, sensitivity was 74.3% and 71.4%, and specificity 79.8% and 88.7%, respectively. Using a combined cut-off value of Qmax of 1 5 mL/s or less and PdetQmax of more than 20 cm H2O, sensitivity was 74.3% and specificity was 91.1%.

Based on this prospective, controlled study, preliminary cut-off values were obtained for refining the definition of outlet obstruction in women.