Female urinary incontinence

The three main subtypes of UI are:

• Stress urinary incontinence (SUI): involuntary leakage on effort or exertion, or on sneezing or coughing;
• Urgency incontinence (UI): involuntary leakage accompanied by, or immediately preceded by, a sudden compelling desire to pass urine which is difficult to defer (urgency); and
• Mixed urinary incontinence: involuntary leakage associated with both urgency and also physical stress (exertion, effort, sneezing, or coughing). Mixed UI may be stress or urge dominant.

Other types of incontinence:

• Overflow incontinence/chronic urinary retention: occurs when the bladder cannot empty completely and becomes over distended;
• Nocturnal enuresis: involuntary leakage of urine during sleep;
• Functional incontinence: incontinence where no organic cause is found.

Urinary frequency is generally considered as ≥ 8 micturitions during waking hours, though this number is variable depending on hours of sleep, fluid intake and co-morbidities.

Overactive bladder syndrome (OAB) is defined as urgency, usually with increased frequency and nocturia, which may occur with or without urgency incontinence. Stress urinary incontinence and overactive bladder syndrome are the cause for over 90% of cases of urinary incontinence.

Figure 1: Physiology of urinary continence

Causes

Urinary continence in females depends on urine being stored in a receptive bladder closed by a competent sphincter mechanism. When the bladder is full, nerve impulses pass to the pontine micturition centre in the brain which triggers urination. The detrusor muscle contracts as a result of acetylcholine acting on muscarinic receptors. Incontinence can occur when there is detrusor instability or a failure of the sphincter mechanism. In addition, there is a complex neural control which co-ordinates urethral and bladder function to alter from storage to voiding at socially acceptable times.

The causes of incontinence in females:

• Childbirth with resultant neuromuscular damage to the pelvic floor;
• Onset of the menopause with oestrogen deprivation;
• Previous pelvic surgery such as hysterectomy in women can weaken the muscles that support the bladder and urethra, increasing the risk of stress incontinence;
• Neurological conditions such as Parkinson’s disease, multiple sclerosis; and
• Pharmacological agents including alpha-blockers, antidepressants, sedatives, ACE inhibitors and diuretics.

Restoration of continence in women affected involves a thorough knowledge of normal functioning anatomy and physiology of the lower urinary tract as only through improved understanding of disease mechanisms can rational treatment be applied.

Figure 2: Incontinence types; Stress, Urge and Overflow

Prevalence

Population studies from numerous countries have reported that the prevalence of UI ranged from approximately 5% to 70%, with most studies reporting a prevalence of any UI in the range of 25–45%. The reported prevalence of UI among women varies widely in different studies due to the use of different definitions, the heterogenicity of different study populations, and population sampling procedures. However, it can be concluded collectively from these studies that prevalence rises with:

• Increasing age;
• More common in women than men (approximately 10% of all adult women suffer from UI);
• Women aged ≥70 years of age (more than 40% of this female population is affected);
• In elderly; and
• Nursing home patients.

Complications

• Skin problems – a person experiencing urinary incontinence can often be prone to skin sores, rashes, and infections. Without effective treatment, urinary incontinence can have an unfavorable outcome. Prolonged contact of urine with the unprotected skin can cause contact dermatitis and skin breakdown. If left untreated, these skin disorders may lead to pressure sores, ulcers and infections such as perianal candidiasis and cellulitis.

• Emotional stress – the inability to retain or the involuntary leakage of urine can often lead to discomfort and embarrassment for the sufferer. Embarrassment can cause people to withdraw socially, and this may lead to depression.

• Urinary tract infections- Patients whose urinary incontinence is treated with catheterisation also face risks. Long-term use of a urinary catheter significantly increases the risk of infection. Also, individuals with a decompensated bladder that does not empty well, residual urine can lead to overgrowth of bacteria and subsequent urinary tract infection (UTI).

• Prolapse – part of the vagina, bladder, and sometimes the urethra can fall into the entrance of the vagina. This is usually caused by weakened pelvic floor muscles.

• Falls and subsequent fractures from slipping on urine.

• Sleep deprivation from nocturia.

• Urinary incontinence is a leading cause of admission to a nursing home when families find it too difficult to care for a relative with incontinence.

Management

Supervised bladder training, pelvic floor exercises, advice on fluid and caffeine intake, and lifestyle advice may all positively impact UI, frequency and OAB.

Pharmacological treatment may also help to improve the symptoms. Antimuscarinics/anticholinergics and the beta-3-agonist mirabegron are some of the available drug treatment options for UI, frequency and OAB. Anticholinergics inhibit binding of acetylcholine at muscarinic receptors in the detrusor muscle, thus reducing involuntary detrusor contractions without disturbing normal voiding.

Antimuscarinics (first line drug treatment as per NICE guidelines) ie fesoterodine, oxybutynin, solifenacin, tolterodine, trospium. The preferred drug as per HSE medicine management publication for UI, frequency & OAB is tolterodine ER (extended-release).

Tolterodine ER: the dose for adults including elderly is 4 mg once daily. In hepatic impairment, the dose is reduced to 2 mg once daily. Adverse effects such as dry mouth, constipation, dizziness are quite common with antimuscarinics. Where there is no/inadequate improvement in symptoms after at least 4 weeks of treatment, or where adverse effects are intolerable, switching to an alternative antimuscarinic or mirabegron is considered.

Mirabegron: a selective beta-3-agonist is recommended as an option for treating symptoms of OAB for people with whom antimuscarinic drugs are contraindicated, clinically ineffective or have unacceptable side effects. The usual adult starting dose of mirabegron is 50 mg once daily.  A reduced dose of 25mg once daily is advised in

• Moderate hepatic impairment (avoid if the person is also taking a potent CYP3A4 inhibitor);
• Mild hepatic impairment who are also taking a strong CYP3A4 inhibitor;
• Renal impairment (GFR 15–29 ml/min); and
• Renal impairment (GFR 30–89 ml/min) who are also taking a strong CYP3A4 inhibitor.

Other drug treatment options include:

Desmopressin: a synthetic analogue of vasopressin and thus acts as an antidiuretic. Desmopressin administration does carry risks such as fluid retention and hyponatraemia. It is advised to limit fluid intake for 1 hour before to 8 hours after taking desmopressin. It is recommended as per NICE guidelines that serum sodium levels should be measured 3 days after the first dose, and if hyponatraemia is suspected, desmopressin should be discontinued. There may be an increased risk of water retention and hyponatraemia if desmopressin is taken concurrently with certain drugs such as; loperamide, carbamazepine, lamotrigine, ​​​​​​NSAIDs, SSRIs.

Duloxetine (Yentreve®): is a dual serotonin and norepinephrine reuptake inhibitor and increases urethral sphincter activation. Duloxetine has demonstrated efficacy in reducing stress urinary incontinence episodes and increasing quality of life. Nausea is the most common adverse event and the main cause for discontinuation. Other common side effects included constipation, dry mouth and fatigue. For the management of symptoms of stress urinary incontinence the recommended dose of duloxetine is 40 mg twice a day. It is recommended that the patient be reassessed after 2–4 weeks of treatment to evaluate the benefit and tolerability of the treatment. If duloxetine treatment is to be discontinued, dose must be gradually reduced over at least 1 to 2 weeks to reduce the risk of withdrawal reactions.

Topical oestrogen i.e. Vagifem®, Imvaggis®, Ovestin®

In women who have gone through menopause, low oestrogen levels may contribute to urinary incontinence. Topical oestrogens should be used in the lowest effective dose to minimize systemic absorption. The British National Formulary advises that the endometrial safety of long-term or repeated use of topical vaginal oestrogens is uncertain. Consequently, treatment should be interrupted at least annually to re-assess the need for continued treatment. If bleeding or spotting appears at any time during treatment, the reason should be investigated. Investigations may include endometrial biopsy to exclude endometrial malignancy.

References available upon request