Voiding dynamics in women: A comparison of pressure-flow studies between asymptomatic and incontinent women

Objectives. To define the normative values for pressure-flow studies in asymptomatic women and to compare them with the values in women with stress incontinence. Methods. Asymptomatic women between the ages of 30 and 70 years were recruited from the community to undergo urodynamic studies (UDSs). Only women with no or minimal symptoms on the Urogenital Distress Inventory Questionnaire, minimal pelvic organ prolapse, and no previous surgery for incontinence were included. The results of the pressure-flow studies were compared with the values from women evaluated for stress urinary incontinence (SUI) between December 1998 and August 2000. Results. Twenty asymptomatic women (mean age 41.7 years) met the inclusion criteria of the 59 who applied. Their pressure-flow data were compared with that of 40 women with symptoms of pure SUI selected from the 415 who underwent UDSs during this period, 16 of whom were found to have SUI during the UDS. The average maximal flow was 17.2 ± 6.7 mL/s in the control population and 22.0 ± 6.8 mL/s among women with genuine SUI during the UDS (P = 0.039). The detrusor pressure at the maximal flow averaged 24 ± 10 cm H₂O and 16.0 ± 8.6 cm H₂O for the control and SUI groups, respectively (P = 0.016). The voided volumes were somewhat higher for the SUI group (330 versus 419 mL, P = 0.041). Conclusions. These findings confirm the normative pressure-flow data in women and suggest that women with stress incontinence void at a lower detrusor pressure. A chronically reduced outlet resistance during bladder filling, which likely contributes to SUI, also appears to affect the voiding phase in stress-incontinent women.