Urinary incontinence Flashcards
What causes urethral smooth muscle contraction & prevents leakage?
- positive stimulus via alpha-adrenergic fibres
- the sympathetic nervous system
What allows passive filling of the bladder?
- inhibition of the detrusor muscle via beta-adrenergic fibres
- the sympathetic nervous system
What nervous system predominates bladder filling?
- the sympathetic nervous system
What nervous system allows voluntary bladder filling?
- the somatic nervous system
What allows sudden or prolonged increases in bladder pressure?
- the somatic nervous system stimulates urethral striated muscle contraction
Which nervous system predominates urination?
- the parasympathetic nervous system
Describe the mechanisms that allow urination
(the detrusor reflex & micturition reflex)
- when the 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
Distinguishing between polyuria, behavioural problems and incontinence
Behavioural
- stress
- pain
- instinct
- cognitive dysfunction
Polyuria
Pollakiuria
= increased urinary frequency
Impaired control of bladder
- neurogenic
- non-neurogenic (anatomical or functional disorder)
What is true urinary incontinence?
- the pt is unaware that they’re leaking urine
- usually due to poor sphincter functionality
- uncommon in cats
What is urge incontinence?
- the pt is aware that they need to urinate but may have lack of control
- can be caused by bladder irritation or seen as inappropriate urination
What overflow incontinence?
- the pt is (usually) unaware that they’re urinating
- occurs when urine pressure within the bladder is greater than the urethra
- considered a ‘voiding’ rather than storage disorder
Causes of neurogenic urinary incontinence
- sacral fracture
- pelvic nerve or pelvic plexus trauma
- lumbosacral disease (IVDD, lumbosacral stenosis, neoplasia)
- sacral malformation
- FeLV - associated incontinence
- generalised peripheral lower motor neurone disease
- dysautonomia
Other CS of neurogenic urinary incontinence
- LMN signs
- often other neurological signs
Causes of non-neurogenic urinary incontinence
- urethral sphincter mechanism incompetence
- urethral hypoplasia
- lower urinary tract inflammation (bacterial cystitis, sterile cystitis, urolithiasis)
- detrusor instability
- ectopic ureter
- partial outflow obstruction (uroliths, neoplasia, polyps)
- patent urachus
- vestibulovaginal stenosis/septum
- primary detrusor atony with outflow
How does a cerebral lesion causing neurogenic incontinence present?
- the bladder can empty normally but often at inappropriate times
How do brainstem-L7 lesions causing neurogenic incontinence present?
- Absent voluntary micturition
- Bladder is hard to express
- Increased urethral sphincter tone
- High volume urinary retention
- Development of automatic bladder
- UMN bladder
How to S1-S3 nerve root lesions causing neurogenic incontinence present?
e.g. damage to the sacral spine/pelvic plexus/tail pull injury in cats
- LMN bladder
- ‘paralytic bladder’
- Absent voluntary micturition
- Bladder is atonic, 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
Automatic bladder
- may develop over time when initial shock has passed
- where sympathetic and parasympathetic pathways enable bladder emptying when threshold is reached
- not under voluntary control
What is the most common non-neurogenic cause of canine incontinence?
- urethral sphincter mechanism incompetence (USMI)
What is the most common presentation/signalment for USMI?
- female
- spayed
- older
- large breed
- overweight
- normally presents as intermittent involuntary leaking of urine when dog is relaxed (sleeping) or excited
- pt may have good/back leaking days
What can USMI occur concurrently with?
- ectopic ureters
Can USMI be congenital?
- yes
- less common
- some may resolve post 1-2 seasons
What is an uncommon presentation/signalment for USMI?
- male entire or castrated dogs
Breed predispositions for USMI
- Irish setter
- Doberman
- bearded collie
- rough collie
- Dalmation
How can USMI be exacerbated?
- intrapelvic bladder position
Factors that affect/contribute to USMI
- low urethral tone / reduced amount of smooth muscle in urethra
- obesity
- hormonal influence (aging or lack or oestrogens change urethral structure)
- intrapelvic bladder position
Medical management of USMI
sympathomimetic agents
- age to mimic the storage of urine phase Phenylpropanolamine; propalin (vetoquinol) and urolin (dechra)
- ~75% respond well
oestrogens
- act on oestrogen receptors in sphincters
- estriol; Incurin (intervet) and enurace (Janssen)
- takes longer to get a response
- can’t use in males/entire bitches or cats
check for UTI regularly
Surgical management of USMI
All referral level surgery
Colposuspension
- for intrapelvic bladders
- reposition of the bladder neck into the abdomen and urethra is moved between vagina and pubic brim
Urethropexy
- urethra is fixed surgically in a new cranial position
Bulking agents
- for submusoca of urethra (collagen injections)
Urethral occluders
- expandable cuffs provide external pressure to urethra
Prostatopexy
- similar to urethropexy
Congenital causes of incontinence
- intersex pts (rare)
- ectopic ureters
How can being intersex affect incontinence?
- may have combination of genital and reproductive organs resulting in different anatomy or functional problem
When is incontinence observed in pts with ectopic ureters?
- shortly after birth
What is an ectopic ureter?
- bladder is bypassed and urine may empty into vagina or urethra
- grossly ureter could look normal but ‘brows’ along bladder submucosa into ‘intra-luminal’ position
- can occur concurrently with other abnormalities
What is common with ectopic ureters?
- secondary infection, including pyelonephritis
Tx of ectopic ureters
- surgical
Anatomical causes of incontinence (not congenital)
- detrusor instability
– an overactive bladder presenting as pollakiruia
– most animals have underling cystitis, irrupting the bladder lining and over stimulating the detrusor reflex = urge incontinence
What is urinary retention?
- a disorder of urine storage and voiding rather than classic incontinence
- pt presents with stranguria or dysuria, and may be attempting to void urine but unsuccessful
Categories for causes of urinary retention
- neurogenic
- non-neurogenic
either:
- detrusor muscle isn’t working well
or
- bladder isn’t contracting against high outflow pressure
Neurogenic causes of urinary retention
- LMN disorder
– sacral region pathology e.g. cauda-equine syndrome, SI luxation - UMN disorder
– sacrum to brain pathology - Detrusor-urethral dyssynergia
- Dysautonomia
– rare, other neuro signs too (CV, GI, etc)
Management of urinary retention
- facilitate bladder emptying
- medicate depending on cause
Non-neurogenic causes of urinary retention
- blockage
– anatomical obstruction
– functional obstruction - trauma to ureters and/or bladder
- detrusor atony
Anatomical obstruction causes of urinary retention
- either within urinary tract or nearby anatomy
- blocked cat: cell plug/crystals
- prostatic dz
- urolithiasis
- tumour
- strictures
Functional obstruction cause of urinary retention
- urethral spasms
Causes of trauma to ureters and/or bladder
- injury to abdomen (ruptured bladder)
- iatrogenic
What is a common cause of detrusor atony?
- over distention of bladder
What is the bladder like with detrusor atony
- distended and flaccid
Can detrusor atony recover?
- yes if acute onset
What do LMN (sacral spine segments, pelvis nerve or pelvis plexus) disorders result in?
(with respect to the bladder)
- detrusor atony and sphincter areflexia
-> loss of perineal reflexes, distended bladder that is easy to express
Examples of LMN disorders
- cauda-equine syndrome
- sacroiliac luxation
- IVDD
- sacrococcygeal trauma (‘tail pull injury’)
- neoplasia
Tx/management of LMN disorders
- Bethanecol (a parasympathomimetic) may improve bladder contractility IF there is some function left
- nursing/home care: manual expression 3-4x daily, cleaning, monitoring for UTI
What do UMN disorders result in?
(with respect to the bladder)
- disruption between the sacral segments and the pontine micturition centre in the brain
-> reflex detrusor contraction (trying to empty bladder)
-> concurrent uninhibited sphincter spasticity (hard to empty past this) - pts often have paresis or paralysis of the hindlimbs and can’t urinate voluntarily
- bladder is large, firm and difficult/impossible to empty early in the disease
- automatic bladder or reflex bladder can develop = automatic emptying of the bladder when full
Tx for UMN disorder: facilitate complete bladder emptying
- urethral smooth muscle relaxants
– alpha antagonists: phenoxybenzamine, prazosin - skeletal muscel relaxants
– e.g. baclofen, diazepam, dantrolene - monitoring for UTIs is important
What is idiopathic reflex dyssynergia
- loss of coordination between the detrusor muscle contracting and relaxation of the urethra
- i.e. the pt is not blocked and the nerves work fine, everything is just irritated and neuromuscular systems aren’t working in a coordinated fashion
How does idiopathic reflex dyssynergia present?
- spurting urine flow
Ddx for idiopathic reflex dyssynergia
- any cause of inflammation to the bladder or urethra
Problems resulting from idiopathic reflex dyssynergia
- bladder may not empty completely
- can result in an overstretched bladder
- which can become atonic
Tx of idiopathic reflex dyssyngeria
- short term: tx any underlying cause, prevent over distention (tube cystotomy/catheter)
- help restore normal detrusor contraction (parasympathomimetic agents)
- may improve spontaneously or require meds long-term
Most common presentation/signalment for idiopathic reflex dyssynergia
- male dog
- large breed
