Disorders of micturition

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Disorders of micturition

• Stephen P. DiBartola, DVM
• Department of Veterinary Clinical Sciences
• College of Veterinary Medicine
• Ohio State University
• Columbus, OH 43210

The Nephronauts
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Disorders of micturition
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Normal and abnormal micturition

• Normal micturition (urination)
• Filling phase
• Emptying phase
• Incontinence
• Loss of voluntary control of micturition
  (urination)

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Micturition Emptying phase
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Micturition Filling phase
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Micturition Role of somatic nervous system
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Disorders of micturition

• Non-neurogenic
• Neurogenic

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Non-neurogenic disorders of micturition

• Hormone-responsive (?)
• Anatomic abnormality
• Paradoxical (obstructive)
• Post-prostatectomy
• Post-perineal urethrostomy
• Urge incontinence with UTI
• Sphincter mechanism incompetence

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Hormone-responsive urinary incontinence

• Estrogen-responsive in female dogs
• Testosterone-responsive in male dogs
• Same as sphincter mechanism incompetence or an
  overlapping syndrome?

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Non-neurogenic disorders of micturition

• Anatomic abnormality
• Ectopic ureter MOST common
• Others much less common

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Ectopic ureters in dogs

• Young (lt 1 year) at presentation
• Female gt Male
• Siberian huskies, Labrador retrievers, Golden
  retrievers, others
• Unilateral (67) or bilateral (33)
• Terminate in vagina or distal urethra

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Ectopic ureters in dogs
Normal ureteral opening

• Usually diagnosed by excretory urography or
  ultrasonography
• Urethrocystoscopy may be gold standard for
  diagnosis

urethra
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Ectopic ureters in dogs
Unilateral
Bilateral
Cannizzo, 2000
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Ectopic ureters in dogs
Fenestrations in ectopic ureters openings in
urethras of female dogs (Cannizzo, 2000)
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Ectopic ureters in dogs

• Often accompanied by other abnormalities
• Hydroureter
• Hydronephrosis
• Urethral sphincter mechanism incompetence
• Bladder hypoplasia
• Renal problems (pyelonephritis, renal hypoplasia)

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Ectopic ureters in dogs

• Surgery controls incontinence in only 50 of
  affected dogs
• Owner must be warned that many affected dogs have
  coexisting sphincter mechanism incompetence and
  may remain incontinent after surgical correction

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Primary sphincter mechanism incompetence in dogs

• Common in large breed spayed females
• Common breeds Doberman, giant Schnauzer, Old
  English sheepdog, Rottweiler
• Maximum urethral closure pressure (MUCP) lower
  and functional profile length (FPL) shorter on
  urethral pressure profile (UPP) in affected dogs
• Bladder neck positioned more caudally on
  radiographs

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Primary sphincter mechanism incompetence Role of
intra-abdominal pressure

• Intra-abdominal pressure increases in lateral
  recumbency
• Increases in intra-abdominal pressure cannot be
  transmitted to bladder neck and proximal urethra
  if these structures are displaced caudally

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Primary sphincter mechanism incompetence
Treatment

• 90 of affected female dogs respond well to
  phenylpropanolamine (PPA)
• 60 respond to estrogens
• Some require both PPA and estrogens

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Refractory sphincter mechanism incompetence
Collagen injection

• 50 response rate
• Response may be improved by adding
  phenylpropanolamine
• Injections can be repeated with similar response
  rate
• Expensive
• Requires technical expertise

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Refractory sphincter mechanism incompetence
Colposuspension

• Moves bladder neck cranially and lengthens
  urethra
• Approximately 50 response rate
• Response rate may be improved by addition of
  phenylpropanolamine in some dogs
• Complications transient dysuria, suture
  breakdown with relapse

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Neurogenic urinary incontinence

• UMN (automatic) bladder
• Lesion cranial to S1-S3
• Partial voiding (local reflex arc intact)
• High residual volume
• Difficult to express (external urethral
  sphincter lacks UMN inhibition)
• Loss of voluntary control

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Neurogenic urinary incontinence

• LMN (autonomous) bladder
• S1-S3 lesion
• Partial emptying when intravesical/intra-abdomin
  al pressure exceeds elasticity of urethra
• Residual volume higher than UMN bladder
• Easy to express manually
• Loss of voluntary control

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Reflex dyssynergy (reflex dyssynergia)

• Detrusor contracts but urethral muscle fails to
  relax

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Reflex dyssynergy a diagnosis of exclusion

• Middle-aged large to giant breed male dogs
• Watch dog urinate (normal stream initiation then
  dribbling and tenesmus)
• Pass urinary catheter to rule out mechanical
  obstruction
• Measure residual urine volume
• Normal lt 0.4 ml/kg
• Dyssynergy Often 20 ml/kg or more

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Reflex dyssynergy Treatment

• Phenoxybenzamine followed by bethanechol if
  necessary
• Prazosin (specific alpha-1 blocker) followed by
  bethanechol if necessary
• Diazepam or dantrolene if suspect striated muscle
  component
• Intermittent catheterization as needed to
  maintain low residual volume
• Complications bladder hyporeflexia, chronic UTI
• Can be frustrating to manage

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Disorders of micturition History

• Signalment
• Young animals ? Congenital disorders
• Middle-aged, medium to large breed female dogs ?
  Sphincter mechanism incompetence

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Disorders of micturition History

• Differentiate loss of voluntary control from
  behavior change or PU/PD
• Ask about hematuria or dysuria
• Ask about previous trauma or surgery

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Disorders of micturition Physical findings

• Observe perineal region in females for wetness or
  odor
• Palpate bladder, urethra and prostate in males
• Perform vaginal exam in females
• Perform complete neurologic examination

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Disorders of micturition Neurologic exam

• Anal tone
• Bulbocavernosus reflex
• Perineal reflex

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Disorders of micturition Other findings

• Observe animal urinating
• Pass urethral catheter to rule out mechanical
  obstruction
• Collect and measure residual volume (normal, lt
  0.4 ml/kg)

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Disorders of micturition Laboratory findings

• Urinalysis
• Urine culture and sensitivity
• Contrast radiography
• Rule out anatomic abnormality
• Ultrasonography

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Disorders of micturitionSpecial procedures
Cystometrogram

• Pressure-volume recording of bladders response
  to filling with fluid or CO2

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Disorders of micturitionSpecial procedures
Urethral pressure profile

• Pressure tracing of urethra as catheter is slowly
  withdrawn from bladder at constant speed

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Urethral pressure profile

• Maximum urethral pressure (MUP) highest pressure
  recorded in urethra
• Maximum urethral closure pressure (MUCP)
  difference between MUP and intravesical pressure
• Functional profile length (FPL) length of
  urethra over which urethral pressure exceeds
  intravesical pressure

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Urethral pressure profile
MUCP
FPL
FPL is most consistent MUCP more variable
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Micturition disorders Treatment

• Neurogenic Correct lesion if possible
• Anatomic Correct lesion if possible
• Paradoxical Relieve obstruction
• Urge Treat UTI

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Micturition disorders Treatment

• Hormone-responsive in females
• Diethylstilbestrol (DES) 0.1 to 1.0 mg PO ? 3-5
  days followed by 1 mg PO q7d
• Premarin 20 ?g/kg PO q4d or 0.6 mg total dose
  q4d
• Adverse effects estrus, perineal alopecia, bone
  marrow suppression

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Micturition disorders Treatment

• Adrenergic agonists (urethral smooth muscle
  stimulants)
• Ephedrine
• Nonspecific agonist ? gt ?
• Dogs 25-100 mg PO q12h to q8h
• Adverse effects CNS stimulation, tachycardia,
  hypertension
• Not used much due to adverse effects

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Micturition disorders Treatment

• Adrenergic agonists (urethral smooth muscle
  stimulants)
• Phenylpropanolamine (PPA)
• ?-adrenergic agonist
• Dogs 1.5 mg/kg PO q12h to q8h
• Effective in 90 of dogs with sphincter mechanism
  incompetence
• Less CNS stimulation than ephedrine and no
  significant effect on blood pressure
• Off the human market

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Micturition disorders Treatment

• Adrenergic antagonists (urethral smooth muscle
  relaxants)
• Phenoxybenzamine
• Non-specific ?-adrenergic antagonist
• 0.25 to 0.5 mg/kg q12h to q8h
• Relaxes urethral smooth muscle
• Adverse effect hypotension
• Used for functional outlet obstruction (including
  reflex dyssynergy)

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Micturition disorders Treatment

• Adrenergic antagonists (urethral smooth muscle
  relaxants)
• Prazosin
• Specific ?-1 adrenergic antagonist
• 0.1 mg/kg divided q8h
• Relaxes urethral smooth muscle
• Adverse effect hypotension
• Used for functional outlet obstruction (including
  reflex dyssynergy)

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Micturition disorders Treatment

• Adrenergic antagonists (urethral smooth muscle
  relaxants)
• Acepromazine
• Phenothiazine with ?-adrenergic antagonist
  effects
• 0.2 mg/kg SQ q12h or 1.25 mg total dose PO q24h
  for post-obstructive urethral spasm in cats
• Relaxes urethral smooth muscle
• Adverse effect hypotension

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Micturition disorders Treatment

• Other non-specific smooth muscle relaxants used
  for detrusor hyperactivity
• Propantheline
• Oxybutynin
• Flavoxate
• Dicyclomine

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Micturition disorders TreatmentSmooth muscle
stimulants

• Bethanechol
• Parasympathomimetic with primarily muscarinic
  effects
• Dogs 5-15 mg PO q8h
• Cats 1.25-5 mg PO q8h
• Adverse effects Anorexia, salivation,
  lacrimation, abdominal cramping, vomiting,
  diarrhea
• Used for detrusor hypoactivity, used in
  conjunction with ?-antagonist in reflex dyssynergy

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Micturition disorders Treatment

• Striated muscle relaxants
• Diazepam
• Used to relax urethral striated muscle
• Dog 2-10 mg PO q8h
• Cat 1-2 mg PO q8h
• CAUTION IN CATS Hepatotoxicity may be observed
  when administered orally
• May have limited effect on feline urethral
  striated muscle

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Micturition disorders Treatment

• Skeletal muscle relaxants
• Dantrolene
• Direct-acting striated muscle relaxant
• Used for urethral striated muscle spasm
• Dog 1-5 mg/kg PO q12h to q8h
• Adverse effects Hepatotoxicity