Contribution of the posterior compartment to the urinary continence mechanism

Objective: To describe the contribution of the posterior pelvic compartment to the urethral closure mechanism. Methods: Urethral profilometry at rest and during stress was performed in 32 continent women before and after inserting a weighted (1 kg) posterior speculum to displace the posterior vaginal wall and levator ani muscles away from the bladder neck and the urethra. Results: Insertion of the speculum decreased the pressure transmission ratios in the proximal quarter of urethra (from 81 to 76; P < .05) and the urethral closure pressure under stress in the proximal two urethral quarters (from 5 to -3 cm H2O in the first and from 12 to 0 cm H2O in the second urethral quarter; P <.05) in all 32 women. Before speculum insertion, 20 women had positive urethral closure pressure in the proximal urethra under stress, and 12 had negative urethral closure pressure in the proximal urethra under stress. In the 20 women with positive urethral closure pressures under stress in the proximal urethra without a speculum, the insertion of a posterior speculum decreased the pressure transmission ratios to the proximal urethral quarter (from 87 to 78; P <.05) and decreased the urethral closure pressures under stress in the proximal two urethral quarters (from 13 to -4 cm H2O in the first urethral quarter and from 24 to 2 cm H2O in the second urethral quarter; P < .01). In the 12 patients with negative urethral closure pressures under stress in the proximal urethra without a speculum, the profilometry values were unchanged by insertion of a speculum. Conclusion: These observations indicate that the posterior vaginal compartment may contribute to the closure mechanism of the proximal urethra in continent women. (C) 1998 by The American College of Obstetricians and Gynecologists.).