Urinary storage and voiding dysfunction

Both urological and neurological problems can cause dysfunction of urinary storage or voiding, causing lower urinary tract symptoms (LUTS).

Anatomy

• The lower urinary tract involves bladder, urethra, and external urethral sphincter
• Has two functions
  • Symptom-free storage of urine which is constantly draining from the kidneys
  • Periodical, voluntary, unobstructed, and complete voiding of stored urine
• Central or peripheral neurological problems can interfere with the carefully coordination of the lower urinary tract
  • Demyelination (MS)
  • Spinal cord lesions

Innervation of the bladder

There are three centres of bladder control in the CNS:

• Frontal cortex – which inhibits the PMC
• Pontine micturition centre (PMC)
• Onuf-nucleus in sacral spine

The muscles involved in urination are innervated like this:

• Parasympathetic fibres from sacral spine innervate:
  • Detrusor muscle, causing contraction
• Sympathetic fibres from lower thoracic level innervate:
  • Detrusor muscle, causing relaxation
  • Internal sphincter, causing contraction
• Somatic (pudendal nerve) fibres from sacral spine innervate:
  • External sphincter, causing contraction

Urinary storage dysfunction

• Caused by
  • Detrusor overactivity (overactive bladder)
    • Neurogenic or secondary to chronic bladder outlet obstruction
  • Low bladder compliance
    • Fibrosis
    • Cystitis with oedema
  • Detrusor and sphincter dyssynergia (DSD) syndrome
    • The detrusor contracts while the external urethral sphincter is contracted -> intravesical pressure increases
  • Weak pelvic floor muscles
    • After vaginal delivery
  • Prostatitis
• Causes storage symptoms
  • Urgency
  • Frequency
  • Nocturia
  • Incontinence

Voiding dysfunction

• Caused by
  • Bladder outlet obstruction
    • BPH
    • Urethral stricture
    • DSD syndrome
  • Underactive detrusor
• Causes voiding symptoms
  • Hesitancy
  • Straining
  • Intermittent urine stream
  • Terminal dribbling of urine
  • Sensation of incomplete voiding

Types of disturbance according to neuroanatomical location

We can distinguish three types of urinary bladder innervation disturbances based on the location of the lesion.

A suprapontine lesion, usually of the frontal lobe, causes loss of voluntary control of the urination. This can occur due to stroke, dementia, etc.

A spinal cord lesion between the pons and the Onuf nucleus causes detrusor-sphincter dyssynergy or detrusor hyperreflexia. This can occur due to multiple sclerosis, myelitis, etc. This is the most common site of lesion.

A subsacral lesion, below the Onuf nucleus, initially causes urinary retention, and later causes overflow incontinence. This can occur due to trauma or herniation, for example as part of cauda equina syndrome.

Types of disturbance according to pathomechanism

In detrusor-sphincter dyssynergy, the detrusor and sphincter muscles don’t contract in a coordinated way, causing the detrusor and sphincter to contract simultaneously, increasing the pressure in the bladder. It is usually seen in spinal cord lesion, and it usually causes urge incontinence.

Detrusor hyperreflexia or hyperactive bladder is usually seen in suprapontine or spinal cord lesion. It usually causes urge incontinence.

Detrusor areflexia or hypoactive bladder is usually seen in subsacral lesion. It usually causes overflow incontinence or residual urine.

Types of disturbance according to clinical features

Urge incontinence is characterised by urinary leak preceded by a strong urge to urinate. The patient usually can’t urinate properly despite the strong urge. It can be due to intravesicular (urological) problems or due to neurological problems. It usually occurs due to bladder hyperactivity or detrusor-sphincter dyssynergy.

Overflow incontinence is characterised by the bladder filling up, causing urine to dribble out. This can be due to a peripheral lesion causing hypoactivity of the bladder, or due to bladder obstruction.

Stress incontinence is characterised by urinary leak when the intraabdominal pressure increases, like when coughing. This is usually not neurological in origin, but rather urological or gynaecological.

Treatment

Urge incontinence:

• Anticholinergics
• TCAs with strong anticholinergic effect (imipramine)
• Alpha blockers
• Beta 3 agonists
• Patient self-catheterisation

Overflow incontinence:

• Patient self-catheterisation

Stress incontinence:

• TCAs with strong anticholinergic effect (imipramine)
• Duloxetine
• Surgery