The effect of vesical volume on Valsalva leak-point pressures in women with genuine stress urinary incontinence

OBJECTIVE: To determine the effect of increasing vesical volume on the Valsalva leak-point pressure, examine the relationship between leakage at a given volume and clinical incontinence severity, and evaluate the relationships between leakage at a given volume and other measures of urethral resistance. METHODS: One hundred twenty women with genuine stress urinary incontinence (GSI) underwent serial Valsalva leak-point pressure determinations at vesical volumes of 100, 200, and 300 mL, and at maximum cystometric capacity. Urinary diary data, quantitative pad testing, and passive and dynamic urethral profilometry were also performed. RESULTS: Thirty-three women had leakage starting at a vesical volume of 100 mL, 18 at 200 mL, and 19 at 300 mL, and 17 had leakage only at maximum cystometric capacity. The mean first positive Valsalva leak-point pressures were significantly higher than Valsalva leak-point pressures at maximum capacity in all groups: in women who began to leak at 100 mL, 57 versus 36 cm H2O (P < .001); at 200 mL, 59 versus 45 cm H2O (P < .001); and at 300mL, 61 versus 47 cm H2O (P = .01). Women who had leakage at lower vesical volumes had worse measures of clinical incontinence severity and lower maximum urethral closure pressure less than or equal to 20 cm H2O) and pure intrinsic sphincteric deficiency (low urethral pressure and the lack of urethral hypermobility), but the specificities were 63 and 50%, respectively. CONCLUSIONS: Women with GSI are more likely to leak during Valsalva with increasing vesical volume. Valsalva leak-point pressures decrease significantly with bladder filling. The volume at which leakage occurs correlates inversely with clinical severity and directly with maximum urethral closure pressure. A negative Valsalva leak-point pressure at 300 mL excludes the presence of low urethral pressure and pure intrinsic sphincteric deficiency; however, the specificity and positive predictive value are inadequate for making a clinical diagnosis of either condition.