Pathophysiology Of Micturition

Front 1

Describe normal reflex voiding in infants:

Back 1

*Bladder storage “problem”

*Stops when brain and spinal cord develop further at 3-5 years old.:
1) Toilet training
2) Brain gains control over voiding through the pons
3) Applies to defecation as well

*Pontine Micturition Center (PMC):
-Dorsal pontine tegmentum.
-Bladder storage and emptying by coordinating bladder parasympathetics (PS) and sphincter somatics.

*Brain is largely inhibitory (promoting urine storage):
-Detrusor control involves brain (right superior frontal gyrus, pons, and sacral spinal cord.

Front 2

What are the components of the sacral spinal cord involved in normal reflex voiding in infants?

Back 2

1) Parasympathetic stretch receptors to bladder.
2) Somatic nerve bodies that innervate external sphincter (ES).

*SPN= sacral PS nucleus
*ON= onuf's nucleus

Front 3

Nervous system pathways of bladder control:

Back 3

Front 4

With toilet training, what does the nervous system do as the bladder fills?

Back 4

*As bladder fills, brain sends inhibitory messages to pontine micturition center (PMC).

*STORAGE:
-PMC sends messages to sacral spinal cord.
-Inhibiting parasympathetic nerve bodies to bladder detrusor.
-Stimulating somatic nerve bodies to external sphincter.

*At capacity, PMC stimulates somatics to ES:
-External sphincter squeezes to keep urine in (“Curtsy Sign”)

*Normal voiding= No urge or reflex voiding.

Front 5

With toilet training, what does the nervous system do when the bladder is full?

Back 5

*COORDINATED VOIDING WHEN BLADDER IS FULL.
*Brain then becomes aware of urge to void & when the time/place is socially acceptable.

*Brain releases inhibition to PMC:
-PMC sends messages to sacral spinal cord, inhibiting somatics to ES (relaxation) and stimulating PS to bladder detrusor (squeeze).
-Sympathetics relax internal sphincter (at BN).
-Sphincter relaxes, bladder squeezes at low pressure, quickly and to completion.

Front 6

Discuss Nocturnal Enuresis in the context of Development of Control:

Back 6

*Bedwetting is a delay in the completion of toilet training.

*Sequence of development of control:
1) Daytime fecal continence
2) Nighttime fecal continence
3) Daytime urinary continence
4) Nighttime urinary continence

*Nighttime control of urine usually comes last.

Front 7

Discuss Nocturnal Enuresis. What causes it? How do we treat it?

Back 7

*Bladder Storage Problem.

*Unclear what is the exact cause:
-Heavy sleeping, hormonal problems (lack of ADH), genetics, small bladder capacity, or psych issues (stress).

*Treatments:
-“Positive imagery”
-Nocturnal alarm to wake up before wets bed.
-DDAVP (synthetic vasopressin); increases water resorption in renal collecting duct.

*Should resolve spontaneously.

Front 8

Describe sensory neuropathy of the bladder:

Back 8

*Pt loses urge to void, forgets to void.

*Urinary retention, overflow incontinence.

*Bladder emptying problem.

*Often seen in diabetes!

Front 9

What's the treatment for Sensory Neuropathy?

Back 9

*Usually there's no motor neuropathy; recommend timed voiding for these patients even if they don't feel like it.

*If there IS motor neuropathy (neurogenic bladder):
-“clean intermittent cath” (CIC): patients cath themselves every 3-4 hours. Yikes!
-Chronic foley.
-Sacral nerve stimulator (photo).

Front 10

Discuss normal bladder physiology:

Back 10

*Normal capacity is 300-400 mL comfortably without uninhibited contractions or increase in bladder pressure.

*Compliance = Δvolume/Δpressure= ∞ (normal).
-Impaired compliance causes increased bladder pressure with small changes in bladder volume.

*Low voiding pressures protect bladder from developing hypertrophy (trabeculation).

-Normal voiding pressures:
*Female- near zero voiding pressures.
*Male- usually <30 cm H2O.

Front 11

What is bladder hypertrophy?

Back 11

*Hypertrophy --> worsening compliance --> high pressures transmitted to kidneys --> renal failure!

*Clinical signs of “too high” pressure: hydronephrosis, VUR.

Front 12

Back 12

Hydronephrosis.
Left: black stuff is extra urine in kidney.
Bottom right: hydronephrosis in both kidneys.

Front 13

What is Neurogenic Detrusor Overactivity?

Back 13

*Remember toilet training model. Brain normally exerts inhibitory control over bladder through pontine control of detrusor and sphincter.

*If brain is damaged or if message from pons cannot travel to sacral cord b/c of spinal cord injury, you no longer have control. Leads to urinary urgency, frequency and urge incontinence--> REFLEX VOIDING.

*This is a Bladder storage problem called "NEUROGENIC DETRUSOR OVERACTIVITY."

Front 14

What kind of lesions cause detrusor overactivity?

Back 14

*Cranial lesions:
-CVA, tumor, brain surgery, Multiple sclerosis (cortical plaques), Parkinson’s disease (basal ganglial lesions).

*Spinal cord lesion or injury above sacral cord.

Front 15

What is the role of Stroke in neurogenic detrusor overactivity?

How would you treat this?

Back 15

*Particularly bad b/c usually impaired mobility which adds to urge incontinence and/or urgency.

*Can inhibit PS with anticholinergic meds.

Front 16

What is Neurogenic Acontractile Bladder?

Back 16

*Compression of sacral spinal cord nerve roots from herniated lumbar disk affect:
-Parasympathetics to bladder, rectum and penis.
-Somatics to perineum.

*Parasympathetic sensory and motor problem: bladder can’t feel or squeeze.

*Anticholinergic effect of narcotic pain meds can make this a lot worse.

*May get better after spinal surgery or stopping pain meds.
-If not, CIC.

*Remember that sacral spinal cord ends at L1-L2 (this does vary).

*Bladder emptying problem= ACUTE URINARY RETENTION.

Front 17

Back 17

*Caude equina syndrome.
*This can be a cause of Neurogenic acontractile bladder (acute urinary retention).

Front 18

Discuss Spinal shock in regards to bladder control:

Back 18

*General CNS functional impairment from injury; lasts weeks to months; usually around 6-8 weeks.

*It causes a bladder EMPTYING problem.

*Urinary retention until spinal shock resolves:
-Treatment: Foley catheter or CIC until then.

Front 19

Back 19

*High grade reflux; can lead to renal failure.

Front 20

What is Autonomic dysreflexia:

Back 20

*Combination of headache and HTN.

*Seen in Spinal lesions above T6.

*Unopposed sympathetic response ESPECIALLY DURING full bladder, fecal impaction, UTI’s, decubiti, other stressors.

*Severe HTN and therefore headache, can cause stroke.

*Often seen with DSD.

*Treatment: avoid these stressors
-For Urinary retention--> foley.

*Rapid onset with permanent bladder and renal damage: These patients used to die from renal failure.

*Biggest clinical issues: recurrent UTIs, decubitus ulcers from constant leakage and poor mobility.

*This is a Bladder emptying and storage problem.

Front 21

Discuss BPH:

Back 21

*Prostatic obstruction causes increased work for detrusor.

*Detrusor becomes trabeculated and thick.

*Bladder capacity can decrease, leading to frequency and nocturia.

*Blockage from BPH/BPE - now referred to as Bladder Outlet Obstruction (BOO).

Front 22

Back 22

*BOO: trabeculated bladder.
*Middle: trabeculated bladder.
*Right: normal bladder.

Front 23

What are the consequences of BOO?

Back 23

*Obstruction can cause:
-Overflow incontinence.
-LUTS (lower urinary tract symptoms).

*This is a Bladder Emptying problem, but can also be a Bladder Storage Problem!
-OVERACTIVE BLADDER (OAB)
-Detrusor overactivity, “Irritable bladder”

*Caused by increased PS input from bladder to brain:
-Irritation from overwork (trabeculation)
-Inflammation
-Cancer
-Neurogenic

Front 24

How do you treat BOO?

Back 24

*Relief of obstructing prostate:
-Medications.
-Surgery: TURP (transurethral resection of prostate).

*Increased PS input may decrease if work decreases.

*May need anticholinergic meds postop.

Front 25

Back 25

Bladder cancer.

Front 26

What are the urinary consequences of bladder cancer? How do you treat it?

Back 26

*There is mucosal irritation from cancer.
*Increased PS input to brain--> urge and urge incontinence.
*Causes a bladder storage problem = Overactive bladder (OAB).
*Treatment: Surgery to resect cancer (TURBT).

Front 27

Back 27

Acute bacterial cystitis

Front 28

What are the urinary consequences of UTI? How do you treat it?

Back 28

*Increased PS input to brain from bacterial inflammation.

*Bladder storage problem = OAB.

*Urinalysis & urine culture.

*Treatment: antibiotics.

Front 29

Discuss Stress urinary incontinence following surgery:

Back 29

*Damage to external urinary sphincter from surgery (prostatectomy).

*Not a bladder emptying problem (no overflow incontinence).

*Although no urgency or urge incontinence, bladder storage problem.

*URINARY INCONTINENCE from incompetent sphincter.

Front 30

What's the treatment for Post prostatectomy incontinence?

Back 30

-Kegels.
-Male sling (shown).
-Artificial urinary sphincter if it's really bad.

Front 31

Back 31

Artificial urinary sphincter.

Front 32

Discuss Stress urinary incontinence (SUI) from childbirth:

Back 32

*Damage to external urinary sphincter from childbirth.

*Bladder storage problem--> STRESS URINARY INCONTINENCE.

*Treatment:
-Kegel exercises.
-Transurethral collagen injection.
-Pubovaginal sling.

Front 33

Back 33

Transurethral collagen injection to increase outlet resistance. For treating stress urinary incontinence in women.

Front 34

Back 34

Pubovaginal slings for stress urinary incontinence in women.

Front 35

Take home points from this lecture:

Back 35

1) Bladder stores:
-Must store enough urine (12-15 ounces/360-450 cc) to avoid frequency, urgency and incontinence.

2) Bladder empties:
*Must do at low pressures to avoid renal damage.
*Must do completely to avoid retention.

3) Involves coordination of cortex, pons, spinal cord, bladder and sphincter.

*Lesion above brainstem (in cerebrum/cerebellum/basal ganglia): NEUROGENIC DETRUSOR OVERACTIVITY: Lesions above lead to ‘coordinated incontinence,’ Lesions below lead to incoordination (or DSD).

*Spinal cord lesion above T6 and below brainstem:
1) NEUROGENIC DETRUSOR OVERACTIVITY & DSD (also dyssynergia of internal sphincter- above T8).
2) AUTONOMIC DYSREFLEXIA

*Spinal cord lesion between T6 and S2: NEUROGENIC DETRUSOR OVERACTIVITY & DSD (synergy of internal sphincter- below T8).

*Lesion below sacral spinal cord (S2) or nerve root trauma--> ACUTE URINARY RETENTION.

*In bladder:
-Tumor, infection/inflammation, stones, trabeculation, or other injury can lead to overactive bladder (OAB).
-Obstruction can cause retention.