What causes stress incontinence?

Stress incontinence can occur in both men and women but is particularly common in women.

Damage to the pelvic floor urethral sphincter during pregnancy and childbirth, particularly if the child was born vaginally or vaginal delivery was tried before an emergency caesarean section, can result in a weakened pelvic floor support mechanism and/or pelvic organ prolapse (POP) .

Other causes include:

• Increased pressure in abdomen, as seen with pregnancy, obesity or problems like ascites.
• Vaginal atrophy, atrophic vaginitis, sphincter incompetence and pelvic floor muscle weakness is associated with the menopause.
• Sphincter damage following prostatectomy, trauma, radiotherapy, sacral cord lesions.
• Neurological damage with conditions such as multiple sclerosis and spinal cord injury.
• Damage to the bladder or nearby area during surgery, such as following hysterectomy or prostatectomy.
• Connective tissue disorders, such as Ehlers-Danlos syndrome.

Contributing factors

Contributory factors relating to stress incontinence include:

• Obesity
• Chronic constipation
• Chronic cough — is there a cause for the cough, such as smoking or medication like ACE inhibitor?
• Occupational or recreational activities, such as heavy lifting or high impact sports
• Drugs, such as alpha blockers (eg doxazocin or prazosin) prescribed to lower blood pressure, can relax the urethral sphincter

Bladder and the pelvic floor

In a normal relationship between the bladder and the pelvic floor, while at rest, part of the bladder neck sits above the pelvic floor. When the pelvic floor and sphincter are contracted the urethra is tightly closed, maintaining continence.

With activity, like coughing, there is in increase in the intra-abdominal pressure. To maintain continence there is a reflex contraction of the pelvic floor to equalise the increase in intra-abdominal pressure from the cough. This reflex contraction tightens the urethral sphincter and maintains continence.

The relationship between the bladder and bladder neck changes when there is pelvic floor weakness causing stress incontinence.

With weakness of pelvic floor muscles, the bladder neck prolapses down through the pelvic floor. This saggy pelvic floor no longer effectively supports the bladder and the pelvic floor muscles do not keep the urethra tightly closed.

Coughing causes an increase in intra-abdominal pressure but the reflex contraction fails to contract the saggy pelvic floor effectively.

The pressures are not equalised and the intra abdominal pressure is higher than the urethral pressure. This results in urine squirting at the instant the pressure is increased.

Symptoms of stress incontinence

The key symptoms of stress incontinence are:

• Loss of small amounts of urine – related to increased intra-abdominal pressure from physical exertion, coughing, sneezing, standing up, jumping, running, skipping
• Urine ‘squirts’ out
• Usually a small volume, wet patch on pants
• No urgency

Diagnosis

To diagnose incompetent urethral sphincter and stress incontinence, assess for:

• A normal bladder voiding pattern
• Wet episodes corresponding to an activity causing an increase in intra-abdominal pressure

Clinical practice point. The urine ‘squirts out’ at the time of the increase in pressure, this can be demonstrated by a physical examination.

When the individual has a full bladder, request them to cough and observe for leakage from the urethra. If no leakage is seen on lying down repeat the test when standing. With a stress leakage, the wetting/squirt, occurs at the time of the cough.

If a delayed leakage is observed this is not related to weak pelvic floor muscles, it is likely to be related to a detrusor muscle contraction which has been provoked by the cough and is the result of an overactive bladder.