Physiology of Micturition

1
Physiology of Micturition

• Hann-Chorng Kuo
• Department of Urology
• Buddhist Tzu Chi General Hospital, Hualien

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Neuroanatomy of Micturition

• Storage Stability and good compliance of Bladder
• Empty Contraction of detrusor and opening of
  Urethra
• Parasympathetic - Pelvic nerve
• Sympathetic - Hypogastric nerve
• Somatic nerves- Pudendal nerve

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Neuroanatomy of Lower Urinary Tract
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Neuroanatomy of Micturition

• Micturition reflex center sacral cords 2-4
• Micturition control center pons
• Sensory motor center frontal lobe
• Limbic system
• Cerebellum, Basal ganglia

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Neuroanatomy of Micturition
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Sensory Afferents

• A-delta fibers Micturition reflex, stretch and
  fullness sensation
• C-fibers Noxious sensation, capsaicin sensitive
  primary afferents (CSPA)
• Dual sensory afferents in mammalian urinary
  bladder

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Dual Sensory Innervation of Urinary Bladder
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Storage of Urine

• Stable bladder
• Good compliance
• Competent urethra- mucosa, submucosa, smooth
  muscles, striated skeletal muscles (external
  sphincter)
• Good pressure transmission and hammock effect
  during stress

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Stable Bladder in Filling Phase
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Positive Pressure Transmission during Coughs in
UPP Tracing
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Poor Pressure Transmission during Coughs in
Stress UPP
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High Leak Point Pressure in SUI with good Hammock
Effect
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Empty of Urine

• Sustained detrusor contraction- cholinergic
  parasympathetic fibers
• Relaxation of bladder neck alpha-adrenergic
  sympathetic nerves
• Relaxation of external sphincter- cholinergic
  pudendal nerves
• Patent non-obstructive urethra

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Detrusor Contraction during Voiding Phase
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Bladder Outlet Obstruction during Voiding Phase
in Man
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Bladder Outlet Obstruction during Voiding Phase
in Woman
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Neurophysiology of Micturition
Reflexes
????PONS
??? T10-L2
?????
?? S2,3,4
??
???
???
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Modulation of Sympathetic nerves in
Parasympathetic Ganglion
???????
T10-L2?
??S2,3,4????
SIN
??????
??????
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Innervation of Lower Urinary Tract

• Bladder- cholinergic parasympathetic-
  contraction beta-adrenergic NO relaxation
• Bladder neck alpha-adrenergic- contration
• Urethral muscles- cholinergic parasympathetic,
  NO, cholinergic somatic nerves

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Physiology of Urine Storage

• First sensation of filling
• Fullness sensation
• Urge sensation
• Premicturition urge sensation- phasic detrusor
  contraction
• Increased activity of urethral sphincter during
  filling

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Urodynmic Tracing in Micturition
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Initiation of Micturition- Relaxation of External
Sphincter
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Sustained Detrusor Contraction- Urethrovesical
Reflex

• Stretch receptors in urethral wall
• Detrusor overactivity in urgency- frequency
  syndrome and SUI
• Role of incompetent bladder neck
• Low detrusor contractility in incompetent
  urethral sphincter after prostatectomy

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Micturition detrusor pressure- depends on
urethral resistance

• High voiding pressure indicates a greater
  urethral resistance
• Low voiding pressure indicates a lower urethral
  resistance or a low detrusor contractility
• Efficient bladder empty depends on a sustained
  detrusor contraction

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Detrusor instability and Inadequate contractility
(DHIC)
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Low Detrusor Pressure in Woman with SUI
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Low Detrusor Pressure and BOO
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Detrusor overactivity and BPO
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Efficient Bladder Empty

• Hypersensitive bladder- low detrusor
  contractility
• Inadequate contractility in elderly
• Bladder outlet obstruction- Bladder neck
  dysfunction, Prostatic enlargement, Urethral
  stricture, Cystocele, External
  sphincter dyssynergia

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Urethral Stricture and BOO
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Anterior Urethral Valve and BOO
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Cystocele and BOO
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Autonomic Dysreflexia
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Detrusor External Sphincter Dyssynergia
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Dysfunctional Voiding in Woman
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Pseudodyssynergia in Girl with Incontinence and
UTI
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Pharmacology of Micturition- Increase storage
efficiency

• Reduce detrusor overactivity
• Anticholinergic agents- oxybutynine, flavoxate,
  imipramine
• Ganglion blocker- bentyl
• Beta-adrenergic agents
• Botulinum toxin
• Vanilloid receptor blockers- capsaicin,
  resiniferatoxin

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Detrusor Overactivity after Resiniferatoxin
Treatment
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Initial Excitatory Responses after Capsaicin
Treatment
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Pharmacology of Micturition- Increase empty
efficiency

• Parasympathomimetic agent- Urecholine
• Adrenergic blockers- inhibition of detrusor
  relaxation (?)

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Pharmacology of Micturition- Increase outlet
resistance

• Increase smooth muscle tone
• Imipramine, methylephedrine
• Increase striated muscle tone
• Nitric oxide synthase inhibitor
• Pelvic floor muscle training

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Pharmacology of Micturition- Decrease outlet
resistance

• Decrease bladder neck urethral resistance
• Alpha-adrenergic blockers- dibenyline, terazosin,
  tamsulosin, doxazosin
• Nitric oxide donors
• Botulinum toxin
• Polysynaptic blocker baclofen, diazepam

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Reduction of MUCP after Nitric Oxide Donors (NTG)
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Improved Voiding Efficiency after Botulinum Toxin
Injection
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Decreased MUCP after Botulinum Toxin Injection
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Combination of Medication- Improve Voiding
Efficiency

• Increased bladder sensation- intravesical
  capsaicin, RTX
• Detrusor overactivity- anticholinergic,
  intravesical RTX, botulinum toxin
• Detrusor underactivity parasympathomimetics,
  alpha-blocker, NO donors, striated muscle
  relaxant, periurethral botulinum toxin injection

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Combined Medication Improved Voiding Efficiency

• Urethral sphincter hypertonicity-
  alpha-blocker, NO donors, striated skeletal
  muscle relaxant
• Urethral sphincter overactivity- alpha-blocker,
  striated muscle relaxant, NO donors, botulinum
  toxin
• Bladder neck dysfunction- alpha-adrenergic
  blocker

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Combined Medication- Improved Storage Efficiency

• Detrusor Overactivity- anticholinergics,
  sympathomimetics, imipramine
• Intrinsic sphincter deficiency- imipramine,
  sympathomimetics
• DHIC- depends on voiding efficiency and grades of
  incontinence