Stress incontinence

Stress urinary incontinence (SUI) refers to the involuntary passage of urine when intra-abdominal pressure is raised (for example when sneezing, coughing, laughing, shouting, exercising) and this pressure overcomes the urethral pressure and the mechanisms that maintain continence.

Pathophysiology

For continence to occur, we need to have simultaneous contraction of the urethral sphincters as well as relaxation of the bladder.

Let’s look at these 3 components:

1. External urethral sphincter - controlled by the somatic nervous system with the pudendal nerve (S2-S4).
2. Internal urethral sphincter - controlled by the sympathetic nervous system with the hypogastric nerve (ventral roots of T12-L3).
3. Bladder - the bladder is a complex structure containing the detrusor muscle which contracts during micturition. It is controlled by the autonomic nervous system, specifically the hypogastric nerve of the sympathetic nervous system as well as the pelvic nerve (S2-S4) of the parasympathetic nervous system. The sympathetic arm maintains continence while the parasympathetic arm allows for contraction of the detrusor muscle → micturition.

Continence is also supported by the pelvic floor muscles. These are a group of muscles that form a hammock-like structure at the base of the pelvis. Their role is to support the pelvic organs such as the bladder, uterus, rectum. They play an important role in urinary continence, faecal continence, sexual function and pelvic stability.

The pelvic floor is comprised of:

• Levator ani muscles - this is a group of 3 muscles which stabilises the abdominal and pelvic organs as well as controls the opening of and closing of the levator hiatus. The 3 muscles that make up the levator ani include:
1. Puborectalis
2. Pubococcygeus
3. Iliococcygeus

The urethra and rectum are normally closed at the levator hiatus, however, during urination and defamation the muscle relaxes and continence is overcome. The innervation to the levator ani muscles is supplied predominantly by the nerve to levator ani (S4) and to a lesser degree the pudendal nerve.

• Coccygeus muscles - located at the posterior aspect of the pelvic floor it acts to support the pelvic floor and its overall strength. It is also innervated by the pudendal nerve.

So what happens to cause stress incontinence?

• Weakening of the levator ani muscles with age and overuse.
• Trauma of childbirth or surgery (such as a hysterectomy in women or radical prostatectomy in men).
• A lack of oestrogen after menopause also leads to muscle weakness and deficiencies with the connective tissue supporting the pelvic region.

In all of these instances, there is reduced support of the abdominal and pelvic structures which ultimately ends up in urinary incontinence.

⚠️ Risk factors

• Childbirth - especially vaginal birth. This is because childbirth causes injury to pelvic floor muscles and connective tissue → prolapse. It also causes nerve injury which can lead to muscular dysfunction.
• Hysterectomy - the uterus itself is a supportive organ for the pelvic floor. Thus when it is removed, the pelvic floor is weakened, the bladder and urethra change positions (making incontinence more likely), and nerve damage is also possible during surgery. Another aspect to consider is a decrease in oestrogen levels if accompanied by an oophorectomy as this leads to urethral atrophy → incontinence.
• Increasing age
• Constipation - due to the repetitive pressure on pelvic tissue, this leads to weakening of the muscles.
• Obesity - excessive weight leads to stretching and weakening of the muscles.
• Menopause - again leads to atrophy of the urethra which reduces the pressure which it can sustain.
• Family history
• Chronic cough - as this leads to increased intra-abdominal pressure which can apply repetitive pressure on the urethra. This may be due to smoking or even in cases of ACE inhibitor usage.

🔍 Investigations

It is important to take a detailed history and perform a pelvic examination.

During the pelvic examination we should:

1. Ask the woman to cough with a full bladder. If there is leakage it is highly suggestive of SUI.
2. Assess pelvic floor tone by asking the woman to squeeze your finger during a bimanual examination.

We can grade the strength of the pelvic floor using the Oxford grading system which ranks the strength from 0-5:

We should also assess the severity by asking how often she is incontinent, how often she passes urine, and if she uses pads or has to change clothing. We should also ask them to keep a bladder diary for 3 days minimum to document the amount, type and timing of fluids drank, the voided volume passed, the frequency of micturition, activities causing incontinence and any pad or clothing changes.

🧰 Management

NICE’s recommendations for management of SUI involves lifestyle advice, pelvic floor exercises, surgical treatment and medical treatment. Let’s discuss these in more detail:

🧰

Managing stress urinary incontinence:

💬 Lifestyle advice

• Weight loss
• Reduce fluid intake

🥇 Pelvic floor exercises (Kegel exercises)

A 3 month trial of pelvic floor exercises should be undertaken. This is the first-line option of management. This involves 8 contractions of the pelvic floor done 3 times a day (total of 24 contractions daily). If it proves successful the patient may continue to this line of management. A patient leaflet on how to perform pelvic floor exercises should be done.

→ If the lady is unable to actively contract her own pelvic floor muscles then we can consider electrical stimulation and/or biofeedback (helps identify where the muscles are and how to stimulate them).

To perform the exercises, advise them to lie down and place their finger in their vagina and then to squeeze as if they are trying to stop urine from coming out. They should feel tightness on their finger.

🥈 Surgical management

If conservative management doesn’t work, we can consider:

• Open colpsuspension - the abdomen is opened and the bladder neck is lifted upwards by stitching the lower part of the front of the vagina to a ligament behind the pubic bone. This lift helps to prevent leakage by improving pressure transmission and compression of the neck of the bladder.
• Autologous rectus fascial sling - this involves using a strip of the rectus fascia from the lower abdomen and using it as a sling around the bladder neck and urethra.

🥉 Medical management

• Duloxetine - this is a SNRI that can be used for women who are not able to undergo surgery or opt against surgery. It is believed to work by increasing the pudendal nerve activity thus improving its function.

Adverse effects include: nausea, dry mouth, fatigue, constipation. There are also risks of violence and suicidal ideation associated with it and for this reason it may be considered more harmful than useful.