urethral incompetence Flashcards
neural control of micturition
- when the bladder is full, stretch receptors in the wall of the bladder send nerve impulses to the sacral region of the spinal cord
- by way of a parasympathetic response, signals return to the bladder and stimulate contraction of the muscle of the bladder, and relaxation of the internal urethral sphincter
> this part of the reflex is involuntary and is predominant in the young
<><> - as the CNS matures, it acquires voluntary control over the external urethral sphincter
> urination is controlled mainly by the micturition centre in the pons
> this centre receives sensory information from the bladder, and communicates with the cortex about the appropriateness of urinating at the moment
> at times when it is not convenient to urinate, this centre send back an inhibitory signal to keep the sphincters closed and prevent voiding.
<><> - when appropriate, the spinal cord tell the bladder to contract, and sphincters to open
Urinary incontinence - two large categories of bladder incontinence, and subcategories
Bladder Overflow
◦ Urethral obstruction
◦ Detrusor Atony
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Impaired bladder storage
◦ Urethral incompetence
◦ Ectopic ureters
Urethral Incompetence
- signalment, signs
- origin?
- what about puppies?
*Middle-aged to older spayed female dogs
*Signs: Incontinence when asleep or relaxed
*Origin?
> Lack of estrogen or testosterone → Decreased urethral muscle tone
> ↑ collagen in urinary tract
*In puppies: congenital? +/- ectopic ureters
Urethral Incompetence - how common? when do we see signs after spay?
breed differences?
when to spay?
- other diseases that can contribute?
*5 to 20% of neutered bitches
*Signs 3-4 years after spay
*Large-giant breed or large size mongrels (>20kg:30%- <20kg:9%)
*Spay ˂ 1 y old for medium size dog (≥25kg)
*Tail docking (3.9 times more at risk)
*Presence of concurrent disease inducing PUPD
Urinary Incontinence Predisposing Factors?
- type of desexing surgery?
- age at sapy?
NO influence of
> Type of surgery (ovariohysterectomy vs ovariectomy)
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Conflicting results on
> Age at spay
Age of Spay and Urinary Incontinence - general guidelines / considerations
what about male dogs?
- Conflicting results from different studies
- Bitches expected to be >25kg later- Spay later in their first-year may ↓ the risk of incontinence
- Median time from neuter to clinical signs of incontinence is 3.73 years (5-5417 days)
- Male dogs clinical when older
Diagnostic of Urethral Incompetence - what evidence do we consider?
what tests can we use?
- History
- Normal physical exam
- Check urine specific gravity
> If inappropriately low (maybe no need to treat long term)
<><>
Diagnostic of Exclusion
<><>
Rule out
◦ Urinary inflammation
◦ Urinary tract infection
◦ Calculi
→ Urinalysis
→ Urine culture
→ Radiographs/Ultrasound
Ideal Urethral Pressure Profile - what is this test?
- used in practice?
test that is used in research, not used clinically, but is a definitive test for urinary incontinence
> rather do a treatment trial in practice
EXAM
Treatment for incontinence
- Alpha adrenergic treatment (phenylpropanolamine) effective in males and females
- Severe cases : combination with hormone supplementation
how the alpha adrenergic work for incontinence?
sympathomimetic effects > sympathetic nervous system is responsible for holding urine in the bladder
> in the case of alpha receptors, this is relevant to keeping the internal urethral sphincter closed
Alpha-Adrenergic: Phenylpropanolamine
- what does it do?
- efficacy?
- Increases the urethral tone (alpha Rc)
<><>
Efficacy
◦ 85-90% successful in female dogs
◦ Taper the dose and frequency to find the adequate one to control the clinical signs
Alpha-Adrenergic: Phenylpropanolamine
- side effects and drawbacks
Side effects
◦ Hyperexcitability, panting or anorexia, hypertension ◦ Taper the dose to avoid side effects
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Drawbacks
◦ Expensive
◦ Around 100 dollars per month for a 30kg dog
Diethylstilbestrol (synthetic estrogen) what does it do? how do we administer for urethral incontinence?
- efficiency?
- mechanism
- other drug it works well with?
- side effects?
- 0.1 to 1mg total PO q24h for 3 to 5 days, then same dose 1 to 2 times weekly
- ↑ density and responsiveness of α-adrenergic Rc in urethral smooth muscle
- Efficient in 50-65% of female dogs
- Synergistic effect with phenylpropanolamine
<><><>
Side effects
◦ Estrus-like signs
◦ Myelosuppression (usually reversible if happens)
◦ Endocrine alopecia
Urinary Incontinence treatment - how often is medical management successful?
- estrogen vs alpha adrenergic?
Medical management successful in >80% cases
* Estrogens 40-83% success
* Alpha adrenergic agent 85-97% (less in male dogs ~44%)
incontinence Treatment in Neutered Males? side effects? efficacy?
Testosterone
◦ IM q 3-4weeks
◦ Only 38% dogs continent
◦ 50% no response
<><>
Side effects:
◦ recurrence of benign prostatic hypertrophy
◦ perianal adenoma
◦ behavioral disorders (aggression)
