Micturition

Anatomy that is important to normal micturition?

-Detrusor muscle

-Internal and external urethral sphincters

-Bladder position

-Uretovesicular junction

What kind of muscle is in the urethra?

Smooth and skeletal

2 multiple choice options

urethral sphincter made of smooth muscle

internal sphincter

1 multiple choice option

urethral sphincter made of skeletal muscle that allows voluntary control of urination

external sphincter

1 multiple choice option

What are the three nerves involved in voluntary micturition?

Hypogastric n.

Pelvic n.

Pudendal n.

Where does the hypogastric n. originate on the spinal cord?

cranial lumbar spinal cord

Stimulation of beta receptors by the hypogastric nerve causes

relaxatioin of Detrusor muscle

Stimulation of alpha receptors by the hypogastric nerve causes

increased tone of internal urethral sphincter

The pelvic nerve stimulates detrusor muscle contraction via

Ach

? of the detrusor muscle causes bladder emptying

contraction

1 multiple choice option

somatic nerve that innervates the external urethral sphincter

pudendal n.

where do the pelvic nerve and pudendal nerve arise from on the spinal cord?

sacral spinal cord

which nerve involved in micturition is a part of the sympathetic nervous system?

hypogastric n.

which nerve involved in micturition is apart of the parasympathetic nervous system?

pelvic n.

which nerve involved in micturition is apart of the somatic nervous system?

pudendal n.

What are the two phases of normal micturition?

Storage

Voiding

Phase of normal micturition with sympathetic nervous system dominance via the hypogastric n.

Storage phase

What are the two parts of the voiding phase?

Sensation

Motor

What nerve senses distension of the bladder in the voiding phase?

pelvic n.

What nerve senses pain and over-distension of the bladder in the voiding phase?

hypogastric n.

What is the neural pathway of voluntary voiding?

Pons

Spinal cord

Pelvic n.

Bladder contraction

Urethral relaxation

Inhibition of the ? allows the bladder to contract for voluntary voiding

hypogastric n. alpha receptors

Inhibition of the ? allows the external urethral sphincter to relax for voluntary voiding

pudendal n.

Stimulation of the ? allows the bladder to contract for voluntary voiding

pelvic n.

What are the components necessary for normal storage?

-Ureteral position

-Detrusor relaxation

-Adequate urethral closure/tone

Clinical signs of storage disorders?

-Involuntary leakage

-Voluntary urination normal

-Normal residual volume

What are the components necessary for normal voiding?

-Coordinated detrusor contraction and urethral relaxation

-Unobstructed outflow

Clinical signs of voiding disorders?

-Abnormal voluntary urination

-Stranguria

-Pollakiuria

-Diminished urine stream

-Usually posture

-Increased residual volume

-+/- hematuria

Stranguria is uncommon with ? disorders

storage

1 multiple choice option

Examples of storage disorders?

-Urethral incompetance

-Abnormal destrusor relaxation (detrusor spasm)

-Ectopic ureter

What are the different etiologies of urethral sphincter mechanism incompetence (USMI) ?

-Hormone responsive (USMI)

-Congenital

-LMN disease

What is the most common cause of urethral incompetence?

urethral sphincter mechanism incompetence (USMI)

Most common signalment for urethral sphincter mechanism incompetence (USMI) ?

Young-middle aged, spayed female dogs - usually large breed

Clinical signs of urethral sphincter mechanism incompetence (USMI) ?

-Incontinence at rest

-Months-to-years post spay

-+/- recurrent UTIs

What is the suspected cause of urethral sphincter mechanism incompetence (USMI) ?

Effects of decreased estrogen

how is urethral sphincter mechanism incompetence (USMI) diagnosed?

presumptive/exclusion

urethral sphincter mechanism incompetence (USMI) treatment?

Phenylpropanolamine (PPA)

Estrogen

why is Phenylpropanolamine (PPA) used to treat USMI?

because it is an alpha agonist and increases urethral sphincter tone

3 multiple choice options

cause of urethral incompetence with similar clinical signs to USMI that can be diagnosed with radiographs

pelvic bladder

pelvic bladder treatment?

Phenylpropanolamine (PPA) +/- surgery

What can cause urethral incompetence?

-Urethral sphincter mechanism incompetence (USMI)

-Pelvic bladder

idiopathic and rare storage disorder characterized by sudden voiding with a small bladder

Detrusor instability

Detrusor instability is usually secondary to

inflammation (e.g. infection, cystoliths, neoplasia)

Detrusor instability treatment?

-Treat underlying cause of inflammation

-Enhance relaxation with anticholinergics

What anticholinergics can be used to treat detrusor spasticity?

Oxybutynin

Propantheline

Examples of urethral incompetence storage disorders?

-urethral sphincter mechanism incompetence (USMI)

-pelvic bladder

ectopic ureters are more commonly seen in males or females?

females

1 multiple choice option

clinical signs of ectopic ureter?

-usually present from birth

-constant dribbling in females

-intermittent dribbling in males

how can ectopic ureters be definitively diagnosed?

cystoscopy

intramural ectopic ureter treatment?

laser ablation

extramural ectopic ureter treatment?

surgery

after treatment, animals with ectopic ureters have about ?% residual incontinence due to concurrent USMI

25-50%

Examples of voiding disorders?

Detrusor m. atony

LMN disease

UMN disease

Urethral swelling or urethrospasm

Physical obstruction

? detrusor atony is most common

acquired

1 multiple choice option

What can cause detrusor atony?

-Post-obstruction

-LMN disease of sacral spinal cord

Clinical signs of detrusor atony?

-Large, soft bladder

-Easy to express

-Stranguria with minimal/weak stream

-Large residual volume

-"overflow" incontinence

Diagnostics for neurogenic detrusor atony ?

Complete neuro exam

Imaging

Diagnostics for non-neurogenic detrusor atony ?

-Rectal exam

-Neuro exam

-Imaging: Radiographs to check for stones

Neurogenic detrusor atony tx?

Treat underlying problem

Non-neurogenic detrusor atony tx?

-Relieve physical obstruction

-Address functional obstruction at internal/external sphincter

-Keep bladder small

-Stimulate detrusor contraction

Which class of drug would you use to relax the internal urethral sphincter?

alpha antagonist

Example of a parasympathomimetic drug that can be used to stimulate detrusor contraction?

Bethanechol

do not stimulate detrusor contraction if a ? is present

urethral obstruction

voiding disorder characterized by increased sympathetic or somatic tone with increased outflow pressure

Functional Outflow Obstruction (FOO)

What can cause a Functional Outflow Obstruction (FOO)?

UMN disease

Urethral inflammation

Idiopathic

UMN lesions are cranial to the ? spinal segment

S1

UMN lesions cause loss of ? bladder function

voluntary

Clinical signs of UMN disease Functional Outflow Obstruction (FOO)?

-Difficult to express

-Tetra/paraparesis or paralysis

-Hyperreflexia

-CP deficits

Urethral inflammation or urethrospasm may occur after

catheterization

Clinical signs of Functional Outflow Obstruction (FOO) due to urethral inflammation/urethrospasm?

Stranguria

Pollakiuria

Large firm bladder

Functional Outflow Obstruction (FOO) treatment?

-Alpha antagonist (inhibit internal sphincter)

-Benzodiazepines (inhibit external sphincter)

Clinical signs of physical obstruction?

Stranguria

Pollakuria

Large firm painful bladder

+/- systemic signs

are peripheral nerve lesions common?

no - very rare

1 multiple choice option

peripheral nerve lesion of the pelvic n. would cause

detrusor atony

peripheral nerve lesion of the pudendal n. would cause

external sphincter dysfunction

treatment for incontinence due to UMN lesion ?

Prazosin (alpha antagonist to relax internal sphincter)