Pressure flow analysis may aid in identifying women with outflow obstruction

We refined recently developed pressure flow cutoff values for female bladder outlet obstruction and applied these values in a consecutive group of women undergoing urodynamic testing for various lower urinary tract symptoms.

A total of 87 women with clinical obstruction determined by history and presenting complaint were enrolled in our prospective evaluation of pressure flow studies. We identified 3 groups of participants according to the suspected cause of obstruction, including prolapse in 33, previous incontinence surgery in 25, and no likely source of obstruction identified from history and physical examination only in 29. An additional 124 patients presenting for evaluation of stress urinary incontinence served as controls. Optimal cutoff values for determining obstruction were developed using receiver operating characteristic curves. To determine the prevalence of bladder outlet obstruction these values were prospectively applied to 106 women undergoing urodynamics for various voiding complaints.

In controls the average maximum flow rate was 23 cc per second and average detrusor pressure was 21.9 cm. water, whereas the corresponding values in those with clinical obstruction were 10.7 cc per second and 40.8 cm. water (p <0.001). No differences were noted in the various obstruction groups. Receiver operating characteristics analysis revealed that cutoff values of 11 cc per second or less and 21 cm. water or more optimized the selection of patients with bladder outlet obstruction. Using these values we noted a bladder outlet obstruction prevalence of 20% in a consecutive cohort of women undergoing urodynamic studies at our center.

We propose cutoff pressure flow values for identifying women with bladder outlet obstruction although they should be used only in conjunction with the overall clinical situation. Neither pressure flow data only nor clinical symptoms alone may be sufficient for diagnosing obstruction in women.