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Flashcards in Micturation (Cooke) Deck (46):
1

Detrusor muscle

  • makes up the bladder
  • has tight junctions

2

Urethra

  • 'internal sphincter'
    • has many components
  • external sphincter
    • striated muscle
    • voluntary control of urination

3

Bladder position

  • normal position is important
    • abdominal pressure presses on neck of bladder as well

4

Uretovesicular junction

  • ureters need to be located behind the sphincters for an animal to be continant

5

Receptors in the wall of the bladder

  • Beta receptors
    • stimulation of these receptors cause relaxation of detrusor muscle

6

Receptors in the internal urethral sphincter

  • alpha receptors
    • stimulation causes contraction/inc tone in smooth muscle of urethral sphincter

7

Hypogastric nerve

  • Comes from Lumbar cord segments 1-4 or 5 I think
  • Sympathetic nervous system
  • Excites B and alpha receptors on bladder and internal urethral sphincter
  • sensory functions
    • inflammation
    • stretch

8

Pelvic nerve

  • part of the parasympathetic nervous system
    • primary nuerotransmitter is acetylcholine
  • Comes from Sacral Cord segements 1-3
  • synapses on cholinergic receptors in detrusor muscle
    • stimulation creates contraction of detrusor muscle
  • sensory fibers
    • sense normal stretch of filling bladder

9

Pudendal nerve

  • Comes from sacral segments
  • Primarily somatic and motor fibers to external sphincter
  • some sensory fibers
    • urethra and neck of bladder
  • responsible for voluntary control of bladder

10

Phases of normal micturition

  • Storage phase
    • sympathetic dominance => hypogastric N.
    • plus pudendal nerve => voluntary control
  • Voiding phase (sensory)
    • distention => pelvic nerve
    • pain and overdistension => hypogastric nerve - cerebral cortex
    • pons => to spinal cord => to pelvic n.
  • Voiding phase (motor)
    • coordinated response of
      • bladder contraction
      • urethral relaxation

11

Following the schematic (normal micturition)

  1. Pelvic n. can sense distention
  2. Hypogastric n. can sense pain or over distension - carried up to brain
  3. Brain sends stimulus to hypogastric, pelvic, pudendal nerve
    • inhibition of the hypogastric nerve - inhibition of tone in internal sphincter (alpha receptors)
    • inhibition of pudendal n. for relaxation of external sphincter
    • stimulation of pelvic nerve, release of achetylcholine and contraction of bladder

12

disorders of micturition

Storage disorders 

  • components of normal storage
    • ureteral position
    • detrusor relaxation
    • adequate urethral closure/tone

13

Characteristics of storage disorders

  • Voluntary urination is normal
    • no stranguria, pollakiuria
  • involuntary leakage
  • normal residual volume
    • post urination, blatter should be small 

14

disorders of micturition

voiding disorders

  • components of normal voiding
    • detrusor contraction
    • urethral relaxation
    • physical obstruction

15

Characteristics of voiding disorders

  • voluntary urination abdormal
    • stranguria
    • pollakiuria
    • diminished urine stream
    • usually postures
  • Increased residual volume

16

Clinical approach

  • consider age
    • young: congenital or housebreaking issues
    • adult: acquired

17

Questions to ask on a history

  • When did it start?
  • When does it occur?
  • Urine stream?
  • Awareness?
  • Frequency?
  • Volume?
  • Straining, blood?
  • Other problems?

18

Physical exam elements

  • Bladder size / tone
    • before / after urination
  • Perineal / preputial wetness / staining
  • Rectal exam
  • +/- vaginal exam
    • especially if patient will be sedated for other purposes
  • Neurological exam
    • check anal tone
    • check perineal reflex - retraction if you touch around anus

19

Features of storage disorders

  • Involuntary leakage / urination
    • continuation
    • intermittent
  • Actual urination is normal
    • bladder empties
  • Stranguria uncommon
    • may come about if problem has predisposed animal to urinary tract infections

20

Features of voiding disorders

  • Posturing to urinate
  • Decreased urine passage
  • Large residual volume
  • Stranguria, pollakiuria
  • +/- hematuria

21

Clinical case: Problems - what are DDXs for young adult M-C cat

Stranguria

Pollakiuria

Pigmenturia

Large bladder

Bladder pain

Lethargy

  • Urethral obstruction
    • urethrolith
    • matrix plug
  • Functional obstruction
    • urethrospasm
  • +/- cystitis
    • inflammatory
    • infectious

22

Storage disorders

  • Urethral incompetance
    • hormone resonsive
    • congenital
    • lower motor neuron disease
  • Detrusor relaxation
    • usually secondary
  • Ectopic ureter

23

Urethral sphincter mechanism incompetence 

(USMI)

  • Most common
    • young-middle aged, spayed female dogs
    • large breed > small breed
  • Clinical features
    • incontinence - usually at rest
    • months to years post-spay
    • +/- recurrent urinary tract infections
  • Cause?
    • effects of dec estrogen
      • alpha-adrenergic receptor numbers?
      • inc collagen/ dec muscle?
  • Diagnosis
    • urethral pressure profilometry
    • presumptive
  • TX
    • increase urethral sphincter tone
      • Phenylpropanolamine (PPA) - alpha agonist
      • Estrogen (DES) - maybe upregulate number of alpha receptors
    • other diagnostics
    • other options -
      • urethral occluder
      • bulking agent injections

24

Pelvic bladder

  • Clinical features (zebra diagnosis)
    • similar to USMI
    • maybe void spastically
  • Diagnosis
    • clinical signs + rads
    • R/O other causes
  • TX
    • similar to USMI
    • +/- sx to tack the bladder somewhere...lol

25

Detrusor spasticity

  • Clinical features
    • sudden voiding w/ small bladder
    • usually secondary to inflammation
      • infections
      • cystoliths
      • neoplasia
    • idiopathic
  • DX
    • look for inciting inflammation / infection
    • presumtive
    • +/- cytometrography (rarely done)
  • TX
    • underlying cause
    • enhance relaxation

26

Ectopic ureters

  • Unilateral vs bilateral
  • female > male
  • clinical features from birth
    • females: often constant dribbling
    • males: may dribble intermittently
  • DX
    • cystoscopy
    • contrast radiography (DOUBLE)
    • maybe abdominal U/S first
    • +/- urodynamic testing (rarely done)
  • TX
    • laser ablation (intramural)
    • surgery (extramural, no laser available)
  • outcome
    • 25-50% residual incontinence
      • manage like USMI

27

2 yo, F-s, labrador reriever

leaking urine at night

no other accidents in the house

no stranguria or pollakiuria

previously well house-broken

what is your top differential? TX?

  • USMI
    • used to be housebroken so probs not ectopic ureter
  • alpha adrenergic agonist
    • stimulate the alpha receptors

*ACh-receptor agonist would probably also stimulate bladder contraction, we don't want this

28

Voiding disorders

  • Detrusor contraction
    • atony
    • lower motor neuron dz
  • Urethral relaxation (functional obstruction)
    • upper motor neuron disease
    • urethrospasm
  • physical obstruction

29

Detrusor atony

  • acquired most common
    • post obstruction
    • lower motor neuron dz (sacral cord)
  • Clinical features
    • large, soft bladder
    • +/- easy to express
    • stranguria with minimal / weak stream
    • large residual volume
    • may see 'overflow' incontinence

30

LMN

  • Sacral lesion, or lubar lesion
    • Pelvic/Pudendal nerve
    • trauma
    • cauda equina syndrome
  • distended, flaccid bladder
    • easily expressed
  • dec anal tone / dec perineal reflex
  • +/- paraparesis / paralysis

31

Detrusor atony dx

Neurogenic vs. Non-neurogenic

  • Neurogenic
    • complete neuro exam
    • imaging
      • radiographs
      • myelography
      • CT/MRI
  • Non Neurogenic
    • don't forget rectal exam
    • neuro exam
    • imaging
      • radiographs
        • abdomen
        • caudal urethra
      • +/- contrast
      • cytoscopy

32

detrusor atony - treatment

  • neurogenic - fix underlying problem
  • non-neurogenic
    • relieve physical obstruction
    • address functional obstruction
      • internal sphincter
      • external sphincter
    • reestablish tight junctions
    • keep bladder small
    • stimulate detrusor contraction
      • parasympathomimetic: bethanechol
      • don't do if urethral obstruction present

33

Which class of drugs would relax the internal urethral sphincter?

  • alpha-adrenergic antagonist

*Beta receptors not really on neck of bladder or sphincters

34

Urethrospasm

  • Relatively common post-catheterization
    • especially in cats
  • Clinical features
    • stranguria, pollakiuria
    • large, firm bladder
    • initial normal stream then stops suddenly
  • DX
    • History
    • Clinical signs
    • catheterization: no evidence of obstruction
    • +/- rads: get the whole urethra
  • TX
    • internal sphincter
      • alpha antagonist
        • phenoxybenzamine
        • prazosin
        • tamsulosin: dogs only
    • external sphincter
      • diazepam, alprazolam, midazolam
      • acepromazine

35

Upper motor neuron lesion

  • Lesion crania to S1
    • ​tetra or paraparesis/paralysis
    • hyperreflexia in pelvic limbs
    • CP deficits in pelvic limbs
  • Voluntary bladder function lost, pudendal n. intact
  • sphincter intact: difficult to express
    • +/- loss of inhibition
  • DDX
    • IVDD
    • Trauma
    • Neoplasia

36

Interneurons

  • responsible for reflex arc
  • pelvic n. intact, sense distension
    • impulse can inhibit pudendal nerve and interneurons can travel down pelvic nerve to stimulate bladder contraction
  • Some upper motor neuron dogs can develop a reflex bladder (neurogenic bladder)
    • usually this will be incomplete emptying
    • not conscious

37

Physical obstruction

  • Clinical features
    • stranguria, pollakiuria, +/- hematuria
    • large, firm, painful bladder
    • minimal-no urine passed
    • +/- systemic signs
      • vomiting, anorexia
      • depression, recumbent
      • relative bradycardia-check electrolytes

38

3 yo M-n DSH

lethargy and stranguria for 2 days

PE-large, firm, painful bladder, small amount red urine passed on PE

T: 101.5; P: 100; R: 60

  • This is an emergency
  • Check electrolytes
    • address hyperkalemia
  • Abdominal radiographs
    • get whole urethra

39

Relieving physical obstruction

  • Relieving physical obstruction
    • catheterization is first choice
      • and urethrogram to find obstruction
    • cystocentesis
      • consider risk of bladder rupture
  • If no stones
    • radioluscent stones, tumor, stricture
    • contrast radiography or cystoscopy

40

Peripheral Nerve lesion

  • RARE NEVER RARE NEVER RARE
  • Hypogastric
  • Pelvic => detrusor atony
  • Pudendal => external sphincter dysfunction

41

2 yo, F-s labrador

PC: incontinence

What else do you want to know?

  • When did it start/has it been there all along? - since a puppy
  • When does she leak urine? - continuously
  • Is she aware/does she posture normally? - no
  • Can she urinate normally? - yes
  • Stranguria/pollakiuria? - no

What next?

42

2 yo, F-s labrador

Incontinent

What do you want to do after PE?

disorder, ddx?

  1. Watch urination - normal
  • disorder: Storage dz
  • top ddx: ectopic ureter
    • USMI possible, don't usually leak all the time
    • Pelvic bladder, also don't usually leak all the time

43

5 yo, M-c terrier

PC: unable to urinate

HX:

urethral obstruction 2 weeks ago, urethroliths flushed into bladder and removed, unable to urinate normally since then

PE:

soft, distended bladder, postures, stranguria

WHAT WOULD YOU DO NEXT?

WHAT IS YOUR TOP DDX?

  1. Abdominal radiographs to see if there is a missed stone
    • normal except distended bladder
  2. Pass a urinary catheter to see if it passes easily
    • catheter passes easily
    • bladder easy to express when animal sedated
  • Top DDX: 
    1. Detrusor atony: b/c of hx of obstruction and easily expressible bladder
    2. Urethrospasm
    3. Maybe both

44

Drug for treating Detrusor atony

  • Bethanicol
    • cholinergic

45

Phenylpropanolamine

  • increases urethral sphincter tone

46

3 yo M-c DSH

unable to urinate, hx of urethral obstruction, indwelling catheter for several days, stranguria (passes small amount urine then stream abruptly stops), urinary cath passes easily, no stones on rads

TOP DDX?

TX of choice?

  • Top DDX
    • urethrospasm
  • TX
    • Phenoxybenzamine
      • alpha antagonist to relax urethra and stop spasmings