The vesico-urethral pressuregram analysis of urethral function under stress

About one-third of older multiparous women are prone to stress urinary incontinence (SUI): unwanted urine loss during activities which suddenly raise intra-abdominal pressure. In this paper we describe and test a method for visualizing and analyzing the function of the urinary continence control system (CCS) under stress. Intravesical and intraurethral pressure changes from the resting state were recorded at proximal, mid-, and distal urethral locations during increasingly severe coughs and cross-plotted on a ‘vesico-urethral pressuregram’. The slope (α) and intercept (χ0) resulting from a linear regression analysis of these data were used to develop a continence equation which can be used to predict the equilibrium point pressure (PE): the intravesical pressure at which urine will leak to the intraurethral pressure recording site. We tested the null hypothesis that these parameters would not differ in six young, nulliparous continent women (mean ± S.D. age: 30 ± 3.5 yr) and six multiparous SUI women (52.3 ± 8.0 yr, parity: 1.7 ± 0.8), or between urethral locations. Significant differences in continence equation parameters were found between groups and in different urethral locations. In the SUI group static factors calculated from the term (1 − α) contributed 27% of the mean (S.D.) midurethral PE value, 145 (46) cm H2O, while dynamic factors, estimated from α, contributed 735 of this value. Valuable insights for improving the diagnosis and treatment of SUI may be obtained by analyzing the relative contribution of α and χ0 to urethral closure during physical stress.