Urinary incontinence

• Bladder filling - the sympathetic nervous system predominates

  Positive stimulus (via alpha-Adrenergic fibres) causes urethral smooth muscle contraction (prevents leakage).

  Inhibition of detrusor muscle (via beta-adrenorgic fibres) allows passive filling of the bladder,
• Bladder filling - the somatic nervous system (voluntary)

  Stimulates urethral striated muscle contraction (for sudden or prolonged increases in bladder pressure
• Urination - the parasympathetic nervous system predominates

  When threshold is reached, stretch receptors in the bladder wall stimulate detrusor muscle contraction = detrusor reflex.

  Urethral sphincter muscles relax.

  Micturition reflex = detrusor reflex and inhibition of sympathetic and somatic stimulation to bladder and ureters
• Definition of true urinary incontinence

  The patient is unaware that they are leaking urine. Usually due to poor sphincter functionality (uncommon in cats).
• Definition of urge incontinence

  The patient is aware that they need to urinate but may have lack of control. Can be caused by bladder irritation or seen as inappropriate urination.
• Definition of overflow incontinence

  The patient is (usually) unaware that they are urinating, occurs when urine pressure within the bladder is greater that the urethra. Considered a ‘voiding’ rather than storage disorder.
• Neurogenic causes of incontinence

  Sacral fracture

  Pelvic nerve or pelvis plexus trauma

  Lumbosacral disease (IVDD, lumbosacral stenosis, neoplasia)

  Sacral malformation

  FeLV-associated incontinence

  Generalised peripheral lower motor neurone disease

  Dysautonomia.
• Presentation or neurogenic incontinence

  Sacral spinal cord

  Lower motor neurone disease

  Often have other neurological signs.

  Treatment and prognosis depends on underlying disease.
• Causes of non-neurogenic incontinence

  Urethral sphincter mechanism incompetence.

  Urethral hypoplasia

  Lower urianry tract inflammation (bacterial cystitis, sterile cystitis, urolithiasis)

  Detrusor instability

  Ectopic ureter

  Parrtial outflow obstruction (uroliths, neoplasia, polyps)

  Patent urachus

  Vestibulovaginal stenosis/ septum.

  Primary detrusor atony with outflow.
• Neurological incontinence - cerebral lesions

  Rare, loss of voluntary control.

  The bladder can empty normally but often at inappropriate times.
• Neurological incontinence - Brainstem - L7 lesions

  Upper motor neurone bladder

  Damage to the brain or higher spinal cord.

  Absent voluntary micturition

  Bladder is hard to express

  Increased urethral sphincter tone

  High volume urinary retention.
• Neurological incontinence - S1-S3 or nerve root lesion

  Lower motor neurone bladder

  Damage to the sacral spine/pelvic plexus/tail pull injury in catsAbsent voluntary micturition.

  Bladder is atomic, flaccid and easy to express. Concurrent reduced perineal reflex and anal tone, may have tail paralysis.

  Atonic urethral sphincters

  Absent detrusor reflex

  Can result in overflow incontinence when full.
• Urethral Sphincter Mechanism Incompetence (USMI) - overview

  Most common non-neurogenic cause of canine incontinence

  Normally present as intermittent involuntary leaking of urine when dog is relaxed (sleeping) or excited.

  Can occur concurrently with ectopic ureters.

  Patient may have good/bad leaking days

  May be congenital (less common, and some resolve post 1-2 seasons).

  Can be exacerbated by intra-pelvic bladder position.

  Uncommon presentation: male entire or castrated dogs.
• Urethral Sphincter Mechanism Incompetence (USMI) - medical Management 


  Low urethral tone/reduce amount of smooth muscle in urethra - manage with sympathomimetic agents which aim to mimic the storage of urine phase

  Obesity

  Hormonal influence (aging or lack of oestrogens change urethral structure) - treat with oestrogens which act on oestrogen receptirs in sphincters.

  Intra-pelvic bladder position.
• Urethral Sphincter Mechanism Incompetence (USMI) - surgical management


  Colposuspension - for intrapelvic bladders. Reposition the bladder neck into the abdomen and urethra is moved between vagina and pubic brim.

  Urethropexy - urethra is fixed surgically in anew cranial position.

  Bulking agents - for submucosa of urethra (collagen injections)

  Urethral occluder/s - expandable cuffs provide external pressure to urethra.

  Prostatopexy - similar to urethropexy.
• Anatomical causes of incontinence - Congenital


  Intersex patients (rare) - may have combination of genital and reproductive organs resulting in different anatomy or functional problem.
• Anatomical causes of incontinence - Ectopic ureters

  Incontinence observed shortly after birth

  Bladder is bypassed and urine may be empty into vagina or urethra.

  Grossly ureter could look normal, but burrow along bladder submucosa into intra-luminal position.

  Can occur concurrently with other abnormalities.

  Secondary infection is common (inclduing pyelonephritis)

  Treatment - surgical.
• Anatomical causes of incontinence - detrusor instability

  An overactive bladder presenting as pollakiruria. Most animals have underlying cystitis, irritating bladder, lining and over stimulating the detrusor reflex.
• What is urinary retention?

  A disorder of urine storage and voiding rather than classic incontinence.

  Patients presents with stranguria or dysuria, and may be attempting to avoid urine but be unsuccessful.

  Neurogenic or non-neurogenic categorisation.

  Either:

  • Detrusor muscle isnt working well

  OR

  • Bladder is contracting against high outflow pressure
• Urinary retention - LMN disorder

  Sacral region pathology e.g. caudo-equina syndrome, small intestine luxation.
• Urinary retention - UMN disorder

  Sacrum to brain pathology.
• Urinary retention - detrusor-urethral dyssynergia

  The two aren’t working together, so they might contract at the same time.
• Urinary retention - Dysautonomia

  Rare, other Nuero signs too (CV, GI)
• Urinary retention - blockage

  Anatomical obstruction: either within urinary tract or nearby anatomy

  • Blocked cat: cell plug/crystals
  • Prostatic disease
  • Urolithiasis
  • Tumour
  • Strictures - from old blockages.

  Functional obstruction - urethral spasms.
• Urinary retention - trauma to ureters and/or bladder

  Injury to abdomen (ruptured bladder)

  • Retention just means not being able to excrete urine.

  Iatrogenic
• Urinary retention - detrusor atony

  Often from over distension of bladder; secondary condition we want to avoid.

  Bladder distended and flaccid.

  May reverse and recover if acute onset.
• Lower motor neurone disorders - overview

  Sacral spinal cord segments, pelvic nerve or pelvic plexus results -> detrusor atony and sphincter areflexia.

  Examples:

  • Cauda-equina syndrome
  • Sacro-iliac luxation
  • IVDD
  • Sacrococcygeal trauma (tail pull injury)
  • Neoplasia.

  Loss of perineal reflexes, distended bladder that is easy to express.
• Lower motor neurone disorders - treatment

  Bethanecol ( a parasympathomimetic) may improve bladder contractility if there is some function left.

  Nusring/home care: manual expression 3-4x daly, cleaning, monitoring for UTI
• Upper motor neurone disorders - overview

  Disruption between the sacral segments and pontine micturition centre in the brain.

  • Reflex detrusor contraction trying to empty the bladder)
  • Con current uninhibited sphincter spasticity (hard to empty past this).

  Patients often have paresis or paralysis of the hindlimbs and can not urinate voluntarily.

  Bladder is large, firm and difficult/impossible to empty early in the disease.

  Automatic bladder or reflex bladder can develop = automatic (non-conscious) emptying of the bladder when full.
• Upper motor neurone disorders - treatment

  Facilitate complete bladder emptying.

  Urethral smooth muscle relaxants

  • Alpha antagonists -phenoxybenzamine, prazosin

  Skeletal muscle relaxants

  • Baclofen, diazepam, dantrolene

  Monitoring for UTI is important.
• Idiopathic reflex dyssynergia - overview

  Loss of coordination between the detrusor muscle contracting, and the relaxation of the urethra. Presents a spiriting urine flow.

  Differentials:

  • Any cause of inflammation to the bladder or urethra.
• Idiopathic reflex dyssynergia - Resulting problems

  Bladder may not empty completely

  Can result in an overstretched bladder

  Which can become atonic
• Idiopathic reflex dyssynergia - treatment

  Short-term: treat any underlying cause; prevent over distension (tube cystotomy/ catheter)

  Help restore normal detrusor contraction (parasympathomimetic agents)

  May improve spontaneously or require medication long-term.