Up to 40 % of women in the community are affected by urinary incontinence.
Urinary incontinence can be categorised into different types:
- Stress urinary incontinence (SUI)
- Urge urinary incontinence (UUI)
- Mixed urinary incontinence (MUI)
- Overflow urinary incontinence
- Fistula related
- Functional incontinence
Stress urinary incontinence (SUI)
With stress urinary incontinence (SUI), urine loss is triggered by activity that puts pressure on the bladder e.g., coughing, sneezing, running, lifting, exercise.
As the triggers are usually predictable, people often end up avoiding the activities that cause leakage and restrict their lives. In severe cases of stress incontinence, leakage can occur with minimal activity e.g., walking, standing from sitting and may be associated with minimal awareness of urine loss.
Stress incontinence is caused by weakness of the urinary sphincter (control valve for urination) and pelvic floor muscles and supports of the bladder and urethra.
Urge urinary incontinence (UUI)
In urge urinary incontinence (UUI), loss of urine is associated with a sudden and severe desire to pass urine and often leakage occurs on the way to the toilet. Certain activities can trigger urine loss e.g., putting the key in the door when arriving home, running water, hand washing, cold weather. The volume of urine loss is variable ranging from a few drops to flooding (when the entire bladder volume can be lost). Urge urinary incontinence is usually associated with a more frequent desire to urinate both during the day and at night (also called nocturia)
Some people can experience this type of incontinence without the symptom of urgency in which case urinary leakage can occur suddenly and without any warning.
Urge urinary incontinence (UUI) is caused by detrusor overactivity i.e. the bladder muscle (also known as the detrusor muscle) contracts outside a person’s voluntary control. This bladder contraction usually happens at low bladder volumes and with little warning, unlike a normal bladder muscle contraction.
Detrusor overactivity can be a problem primarily of bladder function or can be caused by the bladder’s response to other conditions (e.g. neurological problems or due to blockage of urine outflow.)
Mixed urinary incontinence (MUI)
Mixed urinary incontinence is a combination of stress urinary incontinence (SUI) and urge urinary incontinence (UUI).
Many people will find that one symptom or the other predominates and is most bothersome requiring treatment first.
Overflow urinary incontinence
Overflow urinary incontinence occurs when the bladder does not empty fully and is chronically over distended. Overflow incontinence does not tend to occur unless bladder emptying is very poor with volumes of 300 ml or more being retained in the bladder after urination.
Overflow incontinence may be associated with a reduced sensation of bladder fullness and feeling of incomplete bladder emptying. It occurs most commonly in the setting of blockage to the outflow of urine (e.g. in men in with prostate enlargement) and in both men and women with poor bladder muscle function (e.g. due to ageing changes in the bladder muscle).
A urinary fistula is an abnormal connection between the urinary tract and another area and is a rare cause of urinary incontinence in Australia and most Western countries. In women, fistulous connections in the urinary tract can occur between the bladder and vagina as well as other parts of the urinary tract (e.g. ureter or urethra).
Trauma from childbirth is the most common cause of urinary tract fistula worldwide. In Western countries fistula is more commonly a result of complications of pelvic surgery.
In cases of functional incontinence, involuntary loss of urine can be caused by physical limitations (e.g. poor mobility and inability to reach the toilet quickly) or cognitive limitations (e.g. memory impairment associated with dementia) that result in an inability to toilet normally.