Micturition Flashcards
What is micturition? Urination?
storage and voiding of urine
voiding urine
What is the difference between urinary incontinence and micturition disorders?
involuntary passage of urine
urinary incontinence and retention
How does urine normally flow?
- produced in kidneys
- ureters undergo peristalsis and deposit urine in the bladder at the trigone
- bladder stores and eventually expels urine
- urine flows from the urethra to the distal urethral orifice, then outside of the body
What are the 2 neurological controls of micturition?
HYPOGASTRIC NERVE - Sympathetic (alpha-adrenergic) innervation Stores urine by relaxing the detrusor and increasing urethral sphincter tone
PELVIC NERVE - Parasympathetic innervation = Pee (void) by activating the detrusor and relaxing urethral sphincter
What occurs in the storage phase of micturition?
sympathetic alpha-adrenergic innervation from the hypogastric nerve causes increased urethral sphincter tone and detrusor relaxation
What occurs in the voiding phase of micturition?
parasympathetic (inhibits alpha-adrenergic) innervation in the pelvic nerve causes relaxation of the urethral sphincter and detrusor contraction
How does the location of neural disease or injury affect micturition?
LMN (sacral) = large, flaccid bladder with decreased tone that is easily expressed
UMN (suprasacral) = large bladder with increased tone that is hard to express
What are 5 causes of large bladders?
- LMN or UMN injury
- detrusor atony - common in blocked cats where prolonged distension damages smooth muscle and neurons
- detrusor-urethral dyssynergia - contraction of bladder and relaxation of sphincter not aligned
- obstruction
- UTI (consequence, rarely cause)
How can the bladder be affected by urinary incontinence?
BIG BLADDER = can’t void urine, which eventually overflows out into the urethra (increased pressure overcomes sphincter)
SMALL BLADDER = urine is not entering the bladder or is not being kept within it
failure of storage
What are 6 causes of small bladders?
- urethral sphincter mechanism incompetence from spay or congenital
- detrusor instability causes urge or overactivity
- ectopic ureters bypass bladder and sphincter
- pelvic bladder - decreased pressure in pelvis unable to keep sphincter closed
- vaginal abnormalities
- UTI - inflammation causes contraction and urges
What is urethral sphincter mechanism incontinence (USMI)? What is the most common sign?
spay / estrogen responsive incontinence most common in FS dogs with a varying onset following their spay (days to years)
positional incontinence —> O usually finds spots on couches or beds, not a constant dribbling
How is urethral sphincter mechanism incontinence (USMI) diagnosed?
r/o other causes and response to treatment
What 4 treatments are available for USMI?
- phenylpropanolamine (Proin) - alpha agonist increases urethral sphincter tone
- estrogen (Incurin, DES) - increases urethral sphincter tone
- collagen injection - bulks urethral sphincter
- hydraulic occluder - cuff around bladder neck with SQ cuff that can be adjusted
What form of USMI is rare? What treatment is recommended?
congenital —> dribbles more often than acquired, may look like ectopic ureters
- phenylpropanolamine (Proin)
- delay spay until first heat
What treatment for congenital USMI is not recommended? Why?
estrogen —> congenital form seen in puppies that are still growing and imbalanced hormones can alter this
What is the most common sign of ectopic ureters?
- BILATERAL = constant dribbling
- UNILATERAL = may void normally at times, since one ureter is still going into the trigone
What are 2 treatments for ectopic ureters?
- surgery - extramural or mural ureter relocation
- laser ablation - less invasive, only doable on mural ureters
How are ectopic ureters diagnosed? What signalment is most common?
- ultrasound
- cystoscopy with catheter follows mural ectopic ureter tunneling through the bladder wall into the urethra
female Labs, Goldens, etc.
How do patients with ectopic ureters commonly present?
- O reports dribbling of urine
- recurrent UTIs, likely due to pooling of urine allowing bacterial proliferation
What things should be considered in patients with possible ectopic ureters?
- historical information: clarify urinary habits
- animal’s age when incontinence first started (birth vs. after spay)
- chronologic course of events
- previous surgeries (neuter, spay)
- use of medication that may stimulate PU
- previous or current UT disease or abnormalities
What should be noted on physical exams in patients with micturition problems?
- bladder size
- genital anatomy: juvenile/recessed vulva common in dogs with congenital USMI
- urine dribbling or urine-stained backend
- lumbar or sacral neurologic abnormalities
What is the normal residual urine volume in dogs? What causes urinary retention?
< 2-3 mL/kg
- urinary tract obstruction
- functional urine retention
What do urinary obstructions do?
prevents urine flow
What are causes of mechanical and functional urinary obstructions?
MECHANICAL - stones, plugs, strictures (congenital vs. acquired from catheterization or stones), TCC tumor
FUNCTIONAL - myelopathies, detrusor urethral dyssynergia (bladder contraction doesn’t correlate with sphincter relaxation), long-standing obstruction
How do urinary obstructions affect serum biochemistry?
postrenal azotemia
What happens when urinary obstructions are not treated?
within 3-5 days, there is atony due to disruption of tight junctions between muscle cells
What is post-obstructive diuresis?
volume expansion from increased pressure caused by urine obstruction impairs tubular function for several days, resulting in massive polyuria for several days
What is the most common urinary obstruction in cats? What are 4 causes?
functional sympathetic nervous input
- neurogenic
- direct irritation of urethra
- anxiety causes increased sympathetic tone*
- urethral spasms
What observations can be made to differentiate functional and mechanical obstructions?
- patient’s ability to void normally
- presence of any straining
- continued or interrupted stream
- full or partial stream
What is seen on palpation of the bladder and rectum in functional or mechanical obstructions?
BLADDER:
- functional = easily expressed, flaccid
- mechanical = hard to express, firm
RECTUM - can palpate urethra for stones, masses, or thickening
What is the best way to differentiate functional and mechanical obstructions?
ability to pass a catheter
- YES = functional
- NO = mechanical (imaging recommended)
What imaging is recommended for diagnosing functional and mechanical obstructions?
- abdominal radiographs: “off the butt” shot in males to get entire urethra —> STONES
- ultrasound (can’t follow urethra)
- contrast radiography or fluoroscopy
- CT with contrast
- cystoscopy
How are urinary stones treated?
- urohydropulsion
- lithotripsy
- laparoscopic
- cystotomy
How are urethra strictures treated?
- bougienage
- balloon catheter
teats scar tissue on the urethra
How are masses causing mechanical obstruction treated?
- radiation, chemotherapy
- laser ablation
What 4 drugs are recommended for treating functional urethral obstruction?
- Phenoxybenzamine, Prazosin, and Tamsulosin - alpha-blockers relax alpha-adrenergic tone to the urethral sphincter
- Diazepam
- Bethanechol - parasympathomimetic activated M receptors on the smooth muscle of the bladder
- Cisapride - smooth muscle contraction (?)
What are the most common clinical signs of FLUT?
- stranguria
- pollakiuria: frequent, small
- hematuria
- periuria: urination outside of litterbox
60% feline idiopathic cystitis, 20-40% urolithiasis, 15-20% UTI + obstructions due to urolithiasis
What is the recurrence of FLUTD like?
50% of cats had a recurrence regardless of cause
- > 50% had more than one recurrent episodes
What is the treatment for feline idiopathic cystitis like? What medications are recommended?
(stress, neurogenic)
- multimodal environmental modification (more litterboxes)
- diet with increased moisture (canned)
- water fountains (may not increase hydration, but cats enjoy playing in them)
- pheromones
- MEDS: Amitriptyline, Gabapentin, Fluoxitine (Prozac)
