Lecture 3 - Micturition

Question 1

internal urethral sphincter

Answer 1

not an actual structure toward the neck of the bladder/urethra

Question 2

external urethral sphincter

Answer 2

striated skeletal muscle structure

Question 3

hypogastric n.

Answer 3

• sympathetic
• beta fibers @ bladder which relax detrussor allowing bladder to distend
• alpha fibers @ neck of bladder or internal sphincter which increase tone, prevent urine from leaking out

Question 4

pudendal n.

Answer 4

• somatic efferent @ external sphincter allows for voluntary control of urination
• alpha receptors @ neck of bladder or internal sphincter to increase tone

Question 5

pelvic n.

Answer 5

• parasympathetic

- ACh receptors @ bladder which causes detrussor contraction

Question 6

storage phase = ______ dominance

explain the role of each nerve

Answer 6

sympathetic dominance

hypogastric n.

• beta receptors relax bladder wall for distention
• alpha receptors increase tone of internal sphincter to prevent leaks

pudendal n.
- alpha receptors increase tone and conscious holding of pee

Question 7

voiding phase = _________ dominance

Answer 7

parasympathetic

Question 8

explain the 3 processes of the voiding phase: sensory, voluntary voiding and the motor voiding phase

Answer 8

sensory

• distention via stretch receptors –> pelvic n. –> brain
• pain –> hypogastric n. –> brain

voluntary voiding: signal of distention reaches brain and brain says its an appropriate time to pee

• pons –> reticulospinal tract –> pelvic n. and pudendal n.
• the bladder must contract and the urethra must relax at the same time!!

voiding phase: motor

• inhibit hypogastric n.: prevents detrustor m. relaxation and allow bladder contraction
• inhibit pudendal n.: prevent contraction of external sphincter and allow urethral relaxation
• stimulate pelvic n.: ACh contracts bladder

Question 9

what are the 3 storage disorders?

Answer 9

1. urethral incompetence (USMI)
2. bladder dysfunction (detrusor spasticity)
3. urethral malposition (ectopic ureters)

Question 10

what are the clinical signs of a storage disease?

Answer 10

involuntary leakage: continuous or intermittent
actual urination is normal
bladder empties
no stranguria

Question 11

what is USMI? what are the clinical features? what is the cause?

Answer 11

USMI = urethral sphincter mechanism incompetence
- usually young-middle aged spayed female, usually large breed

clinical features:
- incontinence
- months-years post spay
+/- recurrent UTIs

cause:

• decreased estrogen causing decreased alpha receptor numbers
• increased collagen/decreased muscle in internal sphincter

Question 12

how is USMI treated?

Answer 12

by increasing uretheral sphincter tone

• phenylpropanolamine (PPA) - alpha agonist
• DES (estrogenic compound) - increases alpha receptor sensitivity

Question 13

what are the clinical features of detrussor spasiticity? how is it dx? how is it treated?

Answer 13

• bladder doesn’t relax appropriately to allow for distention
• sudden voiding of small bladder
• +/- inflammation
• dx is often presumptive; look for inflammation

Tx:

• look for underlying cause
• enhance relaxation via anticholinergics to inhibit the pelvic n. like propantheline

Question 14

what are the clinical features of ectopic ureters? how are they dx? tx?

Answer 14

clinical features:
females - constant dribbling
males - intermittent dribbling

dx:

• contrast rads or CT
• cystoscopy

Question 15

what are the 3 voiding disorders?

Answer 15

detrussor contraction (detrussor atony or upper motor neuron lesion)
urethral relaxation (urethrospasm)
physical obstruction

Question 16

in a voiding disorder, residual volume is _________

Answer 16

increased

Question 17

in a storage disorder, residual volume is _______

Answer 17

normal

Question 18

what are the clinical signs of a voiding disorder?

Answer 18

posturing to urinate
stranguria, pollakiuria
urine passage is decreased
residual volume is increased
\+/- hematuria

Question 19

urethrospasm - how is it acquired? CS? Dx and tx?

Answer 19

relatively common post-catheterization - especially cats

CS: stranguria, pollakiuria, large and firm bladder

dx: looks similar to obstruction but catheterization is easy, rads

tx:
internal sphincter relaxation = alpha antagonist like phenoxybenzamine, prazosin, tamsulosin (in dogs only)

external sphincter = somatic muscle relaxant like benzodiazepam, diazepam, alprazolam, midazolam, ace (all cause sedation)

Question 20

upper motor neuron lesion - what happens? CS? ddx? what can happen over time?

Answer 20

affects urethral relaxation - VOLUNTARY bladder function is lost but sphincter is still intact due to pudendal nerve therefore its difficult to express bladder

CS: paresis or paralysis, hyperreflexia, CP deficts

DDX: IVDD, trauma, neoplasia

over time, can develop ability to empty bladder to degree but cant fully empty

Question 21

physical obstruction: clincal features

Answer 21

stranguria, pollakiuria, +/- hematuria

• large, firm, painful bladder
• +/- systemic signs

emergency! check electrolytes for hyper K!

Question 22

detrussor atony - how is it acquired? clinical features? dx? tx?

Answer 22

acquired via post-obstruction or lower motor neuron disease

CS = general

• large, soft bladder
• easy to express
• stranguria with a weak stream
• increased residual volume after urination

CS = LMN disease

• sacral lesion takes out pudendal and pelvic n. = no anal tone
• distended / flaccid bladder, easily expressed
• decreased anal tone, decreased perineal reflex

dx:
neurogenic = complete neuro exam, imaging: rads, CT/MRI
non-neurogenic = neuro exam, rectal exam, imaging: cysto

tx:
neurogenic = fix underlying problem
non neurogenic - relieve obstruction
- restablish tight junction by keeping bladder small
- leave in-dwelling catheter and stimulate detrusor contraction with ACh agonist (Bethanechol) AFTER obstruction is addressed

Question 23

detrussor muscle

Answer 23

meshwork of fibers in different planes of the bladder that allow it to expand and contract