8. small animal med- micturition disorders

which part of the lower urinary tract consists of smooth muscle?

-detrusor muscle in body of bladder

-extends into proximal urethra and forms internal urethral sphincter

which part of the lower urinary tract consists of striated muscle?

external urethral sphincter

what are the 2 stages of micturition?

1. passive stage

2. active stage

what is the passive stage of micturition?

passive= storage of urine within bladder

-bladder low resistance, high capacity

-urethra high-resistance barrier

what is the active stage of micturition?

active= voiding urine from the body

-bladder high resistance, acts as muscular pump

-urethra low resistance

what are micturition disorders?

any disorder that disrupts the 2 stage process of micturition (passive and/or active stages)

what is the MOA of bethanechol/cisparide?

parasympatheticomimetics (increases smooth muscle contraction)

what is site of action of bethanechol/cisapride?

bladder wall

what is the MOA of phenylpropanolamine?

alpha-agonist (increases tone of smooth muscle)

what is the site of action of estrogens/phenylpropanolamine?

internal urethral sphincter

what is the MOA of prazosin, phenoxybenzamine, and tamsulosin?

alpha-antagonists (decreases smooth muscle tone)

what is the site of action of prazosin, phenoxybenzamine, and tamsulosin?

internal urethral sphincter (decreases tone)

what are diazepam and baclofen used for in micturition disorders (MOA)?

relax the striated muscle of the external urethral sphincter

what should be included in the work-up for animals with urinary incontinence?

-confirm pet is passing urine unconsciously

-r/o infection (UA +/- culture)

-r/o urolithiasis (rads, U/S, contrast urethrogram)

-r/o severe PU/PD (overflow incontinence)

-r/o congenital causes in young animals

what should be included in your PE for urinary incontinence?

1. full neuro exam

2. look for perivulvar or preputial urine staining

3. note confirmation of vulva and perivulvar skin (recessed or hooded vulva, dermatitis)

4. rectal exam (palpate urethra and prostate)

5. observe urination

what are causes of a LMN bladder?

due to sacral lesions or pelvic and pudendal nerves that arise from this segment

leads to urethral and detrusor muscle hyporeflexia

are animals with LMN bladders able to void?

no, unable to void (may leak)

what are defining characteristics of a LMN bladder?

1. distended bladder that is easy to express

2. decreased anal tone and poor perineal reflex

what are causes of a UMN bladder? are they able to void?

due to spinal cord lesion cranial to sacrum

no voiding (bladders become large and may overfill and leak)

do animals with UMN bladders usually have a normal neuro exam?

animals will have a neurogenic functional urethral obstruction with abnormal neuro exam

what are defining characteristics of a UMN bladder?

1. neurologic deficits (paresis and nociceptive loss; ie lack of pain)

2. distended bladder that is difficult to express

what are ectopic ureters?

termination of 1 or both ureters at a site other than the bladder trigone (can be intramural or extramural)

most commonly the urethra, but also vestibule and vagina

what concurrent congenital abnormalities are ectopic ureters commonly associated with?

1. USMI

2. persistent paramesonephric remnants

3. hydroureter/hydronephrosis

4. short urethra

5. vaginal septum or dual vagina

6. hypoplastic urinary bladder

7. renal agenesis or dysplasia

what is the most common signalment for ectopic ureters?

most commonly diagnosed in female dogs (rare in cats)

how do animals with ectopic ureters present clinically?

clinical presentation of urinary incontinence varies:

1. depends on site of termination and concurrent abnormalities

2. often recognized shortly after weaning

3. continuous dripping to intermittent incontinence

4. onset of incontinence can be delayed in male dogs to young adulthood

what is the difference in termination location of intramural vs extramural ectopic ureters?

intramural: in bladder wall

extramural: inserts directly into urethra

Can also insert in vestibule or vagina (but urethra is most common)

what is the species differences between extramural vs intramural ectopic ureters?

dogs: majority are intramural and bilateral

cats: majority are extramural

what should be included in the workup for ectopic ureters?

1. UA +/- culture (UTIs common, proteinuria due to concurrent CKD)

2. chem panel (azotemia)

3. urinary tract imaging

what imaging should be used for working up animals with ectopic ureters?

1. ultrasound to look for ureteral or kidney anomalies and urine jets

2. CT urogram preferred for diagnosis in male dogs

3. cytoscopy preferred for diagnosis in female dogs

what is the treatment for intramural ectopic ureters?

cystoscopic-guided laser ablation, or neoureterostomy (surgery)

what is the treatment for extramural ectopic ureters?

ureteroneocystostomy (can only correct surgically)

what is the prognosis after laser ablation for ectopic ureters?

1. female dogs:

-47% continent

-57% continent with PPA

2. male dogs: 100% continent

what is the prognosis after surgery for ectopic ureters?

1. female dogs: 74% continent with PPA

2. male dogs: 100% continent

what is the most common acquired urinary storage disorder in dogs?

urethral sphincter mechanism incompetence (USMI)

what is USMI?

reduced muscular responsiveness and tone of the urethral smooth muscle

do male or female dogs more commonly get USMI?

neutered female dogs most common

-less common in neutered male dogs

-rare in cats

what are predisposing factors of USMI?

-increased risk of development if neutered before 3 months of age

-pelvic bladders

-short urethra

-recessed vulva (pooling of urine in vestibule during urination)

what is the clinical presentation of animals with USMI?

-wide range of onset (usually within a few years of neutering)

-intermittent continence (especially when recumbent, sleeping, or after exertion)

-USMI occurs when they are relaxed

-increased grooming of peri-vulvar or preputial area

what is included in the workup for USMI?

-diagnosis of exclusion

-UA +/- urine culture

-abdominal imaging (may be normal with USMI)

-r/o urinary tract disease (infection, uroliths, cancer) and other causes of urinary incontinence

what is the treatment for USMI?

medical therapy is the first line of management:

1. female dogs: synthetic estrogens, phenylpropanolamine

2. male dogs: phenylpropanolamine

what are the expected continence outcomes for medical management of USMI?

1. estrogens:

-Female dogs have higher response rate to estriol (89%) compared to DES (65%)

2. PPA clinical response:

-female dogs: 75-90%

-male dogs: 43%

how are animals on PPA for USMI monitored?

hypertension is most common side effect of PPA:

-check blood pressure 7 days after starting, then every 3-6 months thereafter

how are animals of synthetic estrogens for USMI monitored?

recheck CBC in 1 month (if dose too high, can cause bone marrow suppression)

what surgery is performed for treatment of USMI?

artificial urethral sphincter: adjustable hydraulic occluder placed around urethra at neck of bladder

-small SQ port to adjust pressure

-good success for continence

what are complications of artificial urethral sphincters?

risk of urethral obstruction and stricture formation

what is urethral bulking for treatment of USMI?

cross-linked gelatin injected into the urethral mucosa during cystoscopy (successful in female dogs)

what is congenital USMI?

structural or functional abnormality of the internal urethral sphincter

animals commonly have concurrent urinary anomalies

incontinence can be intermitted or continuous, and may still respond to medical therapy

what is reflex dyssynergia?

a functional urethral obstruction

disorder in reflex arc that normally allows urethral sphincter to relax at beginning of urination

how are animals with reflex dyssynergia differentiated from animals with an UMN bladder?

animals with reflex dyssynergia will have a normal neurologic exam (unlike pets with UMN bladder)

what is the typical signalment of animals with reflex dyssynergia?

middle-aged, large and giant breed male dogs most common

what is the typical clinical presentation of animals with reflex dyssynergia?

present similar to mechanical obstruction

postures to urinate and able to produce a urine stream that quickly stops or attenuates

-continues attempt to urinate without emptying bladder

-retention of large amounts of urine leads to overflow incontinence

what is included in the workup for reflex dyssynergia?

contrast urethrography (although it is usually normal)

how is reflex dyssynergia diagnosed?

diagnosis is often presumptive

-observing dog urinate with typical interrupted pattern

-easy passage of urinary catheter

-rule out mechanical obstruction (urethral stone, cancer, stricture)

what is the treatment for reflex dyssynergia?

1. alpha-adrenergic blockage:

-prazosin: alpha-1 receptor antagonist

-tamsulosin: selective alpha-1 antagonist

2. striated muscle relaxant: diazepam, acepromazine, methocarbamol

what is the treatment for reflex dyssynergia for refractory cases?

intermittent sterile catheterization by owners at home

treat bladder atony (increase tone of detrusor muscle):

bethanecol, cisapride

what is the prognosis for reflex dyssynergia?

-good for recovery of normal voiding

-likely require lifelong therapy

-consider tapering meds to lowest effective dose

-urethral stenting for a salvage procedure

what are the typical presentations for feline urinary incontinence?

overall feline urinary incontinence is very rare, 50% of cases are neurologic, and 50% are non-neurologic

what are causes of neurologic feline urinary incontinence?

tail avulsion (tail pull injury) or congenital vertebral canal stenosis most common

what are causes of non-neurologic feline urinary incontinence?

urethral obstruction secondary to urethral stricture most common

should perform contrast cystourethrography for these cases