Disorders of the Female Urinary Tract
• Smooth muscle wall of bladder termed the detrusor muscle
• Normally store 400ml of urine – first urge to void at 200ml
• Micturation reflex – controlled at the level of the pons
o Voiding reflex consists of afferent fibres which pass to the spinal cord and respond to distension of the bladder wall
o Efferent parasympathetic fibres cause contraction of the detrusor muscle
o Meanwhile sympathetic fibres to the detrusor muscle are inhibited
Continence
• Continence depends on the pressure in the urethra being greater than that of the bladder
• Bladder pressure depends on detrusor pressure and intra-abdominal pressure
• Urethral pressure depends on urethral muscle tone and the external pressure evoked by the pelvic floor and the intra abdominal pressure
• Detrusor muscle is expandable – as bladder fills there is no increase in pressure
• Micturation occurs when bladder pressure is greater than urethral pressure
• This is achieved by a drop in urethral pressure (by relaxing the pelvic floor) and increased pressure in the bladder mediated by the detrusor muscle
Incontinence
Causes,
1) Overactive bladder, whereby the pressure exerted by the detrusor muscle in uncontrolled and exceeds that of the urethra
2) Increased intra-abdominal pressure transmitted to the bladder and not the urethra because the upper urethra neck has slipped from the abdomen. This results in bladder pressure exceeding urethral pressure when intra-abdominal pressure is raised. For example in genuine stress incontinence
3) Bypassing of the sphincter mechanism through a fistula
Urinary Tract Investigations
• Urine microscopy, culture and sensitivity – requires a MSU
• Urinalysis – provides info on WBC, nitrites, glycosuria, haematuria
• Urinary diary – patient records for one week vol of fluid intake and micturition
• Post micturition ultrasound or catheterization – excludes chronic urinary retention
• Urodynamic studies
• Cystometry – transdusers are placed in the rectum to measure intra-abdominal pressure and in the bladder to measure bladder pressure. Detrusor muscle pressure in the bladder pressure minus the intra-abdominal pressure. If leakage occur in the absence of detrusor activity the diagnosis is likely to be GSI. If incontinence occurs with detrusor activity the diagnosis is more likely to be ‘overactive bladder’
• Urethral pressure profile – measures maximum urethral closure pressure
• Uroflowmetry – identifies women with poor voiding rates
• Intravenous pyelogram – assesses any fistulas or filling defects
• Methylene dye test – blue dye is instilled into the bladder, looking for fistula
• Cystoscopy – inspection of the bladder cavity
Genuine Stress Incontinence
• Defined as involuntary loss of urine when the bladder pressure exceeds that of the urethral pressure in the absence of any detrusor contraction
• Accounts for 50% of all cases of female incontinence and occurs in 10% of all women
• Aetiology
• Pregnancy, vaginal deliverary with forceps
• Obesity
• Menopause
• Clinical features
• As well as stress incontinence patients may complain of frequency, urgency or urge incontinence. There may also be faecal incontinence due to childbirth injury
• Examination with a Sims’ speculum may reveal a cystocoele or urethrocoele
• Investigations – urine culture to rule out infection and cystometry
• Management
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Conservative
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Physiotherapy and vaginal cones to strengthen the pelvic floor
Surgery -
Aim to allow intra-abdominal pressure to be transmitted to the bladder neck as well as the bladder
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Best procedures at Burch colposuspension and tension free vaginal tape
Overactive Bladder (Detrusor instability)
• Involuntary urine loss due to uncontrolled detrusor contractions either on provocation or spontaneously when patient is trying to inhibit micturition
• Cases 35% of all cases of female incontinence
• Detrusor contraction is normally sensed as urgency. If strong enough it causes the bladder to leak – urge incontinence
• Aetiology
• Commonly idiopathic
• Can follow surgery for GSI
• Multiple sclerosis
• Clinical features
• Urgency and urge incontinence, frequency and nocturia. Possibly urine leakage at night or during orgasm. Faecal incontinence is common as is a history of childhood enuresis
• Examination is usually normal but an incidental cystocoele may be present
• Investigations – urine diary and cystometry
• Management
• Anticholinergics – tolteridine and oxybutynin (side effects, dry mouth, constipation)
• Bladder drill – retraining the bladder
• Synthetic ADH – useful for nocturnal symptoms
• Surgery – clam augmentation ileocystoplasty
Other urinary disorders
• ‘Mixed’ GSI and overactive bladder
o 10% of all incontinence cases
• Acute urinary retention
o Patient is unable to pass urine for 12hr or more
o When catheterised they often produce more urine than normal bladder capacity
o Causes, childbirth (particularly with an epidural), vulval or perineal pain, surgery, anticholinergic drugs, pelvic masses and neurovascular disease
• Chronic retention and urinary outflow
• Accounts for 1% of all cases of incontinence
• Leakage occurs because bladder overdistension eventually causes overflow
• Can be caused by detrusor inactivity (autonomic neuropathies and previous over distension of the bladder) or urethral obstruction (pelvic masses, incontinence surgery)
• Presentation may be similar to stress incontinence or leakage may be continuous
• Upon examination a non tender enlarged bladder may be felt
• Self catheterisation may be required as management
• Sensory Urgency
• Clinical features include urgency, frequency and nocturia with a reduced bladder capacity in the absence of an over active detrusor muscle
• Not often associated with incontinence
• Often seen in post menopausal women
• Maybe caused by stones, infections and tumours, interstitial cystitis or psychological factors
• Fistulae
• Abnormal connections between the urinary tract and other organs
• Most commonly vesico and urethra-vaginal fistulae
• Rare – usually due to surgery, radiotherapy or malignancy