Detrusor Instability and Irritable Bladder

Synonym: overactive bladder syndrome

Detrusor instability is characterised by uncontrolled contraction of the bladder wall (detrusor muscle) producing urgency and sometimes leakage (urge incontinence). Involuntary detrusor contractions cause urgency and urge incontinence, often with frequency and nocturia. Detrusor instability can have a significant impact on quality of life.¹

• Detrusor overactivity is the second commonest cause of female urinary incontinence behind stress incontinence.
• Risk factors include multiple sclerosis and stroke but most cases have no specific cause.
• In men urge incontinence may be due to neurological disease or an enlarged prostate (benign prostatic hypertrophy or prostate cancer).

Usually presents with sudden urge to urinate that is very difficult to delay and may be associated with leakage. Other features include:

• Frequency of micturition
• Nocturia
• Abdominal discomfort
• Urge incontinence

There are no specific physical signs and the diagnosis is usually made from the symptoms and confirmed with urodynamic studies.

• Stress incontinence
• Functional incontinence
• Overflow incontinence
• Urinary fistula
• Enuresis
• Urinary tract infection
• Diabetes
• Bladder cancer
• Bladder stones

• Mid-stream urine M,C and S; to rule out urinary tract infection.
• Investigations to consider differential diagnosis, e.g. renal function, electrolytes, fasting glucose.
• Urodynamic studies show involuntary contraction of bladder during filling.
• Depending on the presentation, ultrasound of the renal tract and cystoscopy may be required.

Incontinence in adults which arises from detrusor instability is managed by combining drug therapy with conservative methods for managing urge incontinence such as pelvic floor exercises and bladder training.² Sacral nerve stimulation is used in patients who do not respond to other treatments.³

Drugs

Anticholinergics, e.g. oxybutynin, propiverine, tolterodine, trospium chloride, have a direct relaxant effect on urinary smooth muscle:^4,5,6

• Antimuscarinic drugs reduce involuntary detrusor contractions and increase bladder capacity.
• There is no evidence of a clinically important difference in efficacy between antimuscarinic drugs.
• However, immediate release non-proprietary oxybutynin is the most cost effective of the available options.⁷
• If immediate release oxybutynin is not well tolerated, darifenacin, solifenacin, tolterodine, trospium, or an extended release or transdermal formulation of oxybutynin should be considered as alternatives.⁷
• The efficacy and side-effects of tolterodine are comparable to those of modified-release oxybutynin.
• The need for continuing antimuscarinic drug therapy should be reviewed after 3-6 months.
• Topical and systemic oestrogen can reduce urinary tract symptoms in post-menopausal women, especially urgency, frequency and dysuria, but is not effective in proven detrusor overactivity.

Surgery

• Surgery is only indicated for intractable and severe detrusor overactivity.
• The most common procedure is an ileocystoplasty, in which the bladder is opened and a patch of ileum sutured into the bladder like a patch.

• May cause severe social difficulties, including shopping, attending meetings, and therefore also social isolation and psychological difficulties.