Urinary continence is maintained by a higher intraurethral pressure than intravesicular (bladder) pressure. Intraurethral pressure is created by the internal urethral sphincter (located at the urethrovesical junction) and external urethral sphincter. When the urethrovesical junction is continuously in the correct anatomic location (ie, nonmobile), any intra-abdominal pressure is transmitted diffusely through the bladder and the proximal part of the urethra, allowing for maintenance of continence.

Stress urinary incontinence (SUI) is involuntary loss, usually drips, of urine during increased abdominal pressure or Valsalva. Examples include coughing, laughing, sneezing, and exercise. Leakage is due to an imbalance of intravesicular and intraurethral pressures. There are 2 ways this imbalance can occur: The most common route is through hypermobility of the urethra, particularly the urethrovesical junction. Less commonly, an imbalance can be caused by intrinsic sphincter deficiency, which is defined as the inability of the urethral walls to close due to weakening of the urethral sphincter muscles.

Risk factors include age, obesity, pregnancy / vaginal delivery, genetics, and pelvic surgery.

About 50% of all women experience occasional urinary incontinence, with about 50% of these women reporting symptoms of SUI. Symptoms can vary from loss of urine a few times monthly to multiple times daily. Depending on the person and situation, leakage of urine can have a significant impact on quality of life.