At rest, continence of urine depends on intraurethral pressure being higher than intravesical pressure. Intraurethral pressure is produced by elastic fibres and engorged urethral venous sinuses. Low intravesical pressure is preserved by bladder muscle relaxation. Urgency incontinence will result if bladder muscle does not relax. A sudden increase in abdominal pressure may overcome this urethral-vesical pressure gradient and cause stress incontinence. The mechanisms that prevent this from happening are unclear. The pressure gradient would not change if the abdominal pressure was transmitted equally to the urethra and the bladder. Continence could also be protected by pressure of the urethra against the symphysis pubis or pelvic muscles. Stress and urgency incontinence cannot be differentiated clinically with certainty. If surgical correction of stress incontinence is planned, preoperative urethrocystometry is mandatory. The Burch colposuspension is the operative procedure of choice. The suspension is done with Prolene sutures; their correct placement is ensured through the use of intraoperative cystostomy.
