Pressure-flow nomogram for women with lower urinary tract symptoms.

Background: Results of urodynamic studies performed in female patients are often difficult to interpret. The objective of the study was to develop a nomogram that would help in diagnosing functional bladder outlet obstruction (BOO) in neurologically intact women with any kind of lower urinary tract symptoms.

Methods: From the urodynamic database adult women were chosen with maximal flow rate (Q max ) ≤ 12 ml/s in a pressure-flow study. Four criteria were used to identify a group of patients suspected of BOO: thickened bladder wall, presence of bladder diverticula, subjective improvement on α-blockers and improvement of voiding symptoms on any form of treatment. The line separating high and low pressure zones on the pressure-flow chart was established according to the position of patients who met at least one of them.

Results: Sixty-seven patientswere investigated. Twenty-one women met at least one of the specified criteria. They had significantly higher voiding pressures (p det(Qmax) 35 cm H2O vs. 16.5 cm H2O; p = 0.002). A new nomogram with one separating line (p det(Qmax) = 1.5 × Q max + 10) was proposed. The difference in the distribution of women fulfilling the criteria between high pressure zone and low pressure zone was highly significant (19/35 vs. 2/32; p < 0.0001). Sensitivity, specificity, positive and negative predictive values of our nomogram in identifying patients suspected of BOO was 90.5%, 65.2%, 54.3% and 94% respectively.

Conclusions: The new nomogram can be considered a screening test which efficiently excludes obstruction among women with low Q max in a pressure-flow study.