Urinary Incontinence

Question 1

How does the bladder store urine?

Answer 1

• Sympathetic nervous system - HYPOGASTRIC nerve
  -Relaxation of detrusor muscle (beta-adrenoceptors)
  -Contraction of urethral smooth muscle + trigone (alpha-adrenoceptors)
• Somatic nervous system - PUDENDAL nerve
  -urethral striated muscle contraction
  -inhibition of the detrusor reflex

Question 2

What occurs during the emptying phase of the bladder?

Answer 2

• Parasympathetic predominates - PELVIC nerve
  -contraction of detrusor muscle
  -relaxation of urethral muscle

Question 3

What is urinary continence?

Answer 3

• Brainstem micturition centre integrates urethral and detrusor function
• Cerebral cortex gives voluntary control by over-riding the
  detrusor reflex
  = holding in urine voluntarily until can go to the toilet

Question 4

Whats first step of investigating urinary incontinence?

Answer 4

• Differentiate between filling + emptying abnormality = Hx

Question 5

What are typical abnormalities of filling phase?

Answer 5

• Patients can urinate normally
• Patients can empty bladder normally
• Patients dribble urine between urinations
• Patients often have reduced bladder capacity

Question 6

What are Ddx for abnormalities of the filling phase?

Answer 6

• Involuntary contractions / urge incontinence
  -cystitis of any underlying cause (bacterial, calculi, neoplasia)
• Reduce pressure at the bladder neck =
  -congenital / acquired USMI
  -Intrapelvic/caudal bladder, hypoplastic bladder
  -Bladder neck mass
• Urine bypassing bladder / part of urethral sphincter muscle = ectopic ureters

Question 7

What are findings in abnormalities of the emptying phase?

Answer 7

• Distended bladder
• Constant dribbling of urine
• No / minimal normal urination of urine

Question 8

What are Ddx for abnormalities of the bladder emtying phase?

Answer 8

• Partial/complete urethral obstruction
• Chronic distension of bladder e.g.=
  -Urethral obstruction (any cause)
  -Pelvic trauma
  -Intervertebral disc protrusion
• Urethral detrusor dyssynergia
  (Dyssynergia = contraction of urethral muscle at same time as detrusor contraction causes a functional urethral obstruction)

Question 9

What is urethral sphincter mechanism incompetence?

Answer 9

• Common condition in bitch uncommon in male dogs + rare in cats
• Commonest cause of incontinence in bitch
• Intermittent involuntary passage of urine when relaxing, recumbent, sleeping
• Dog leaves a patch of urine on bed, carpet …
• Acquired and congenital forms

Question 10

What is aetiology of USMI?

Answer 10

• Low urethral muscle tone
  -reduces with aging, loss of oestrogen (neutering), obesity
• Seen in combination with caudally positioned bladder

Question 11

What is acquired USMI?

Answer 11

• Commonest type of USMI, develops in “later” life
• Usually medium/large breeds =
  -Dobermans, Boxers, Irish setters, Labradors
• Usually seen in neutered females =
  -Onset can be weeks, months/years after neutering
  -Can be worsened by obesity

Question 12

What is congenital USMI?

Answer 12

• Uncommon but important form of USMI
• Juvenile bitches (present prior to 1st season) as incontinent puppies
• 50% resolve after 1st season (don’t neuter these bitches
  until after 1st season)
• Ectopic ureter is main ddx for this condition but dogs with ectopic ureter often also have congenital USMI

Question 13

How would you investigate urinary incontinence?

Answer 13

• Detailed Hx
• Clinical Exam
• Biochem + haematology
• Urinalysis
• Urine culture + sensitivity (cystocentesis)
• Observe urinating
• Imaging = US, plain + contrast radiographs, CT
• Cystoscopy

Question 14

How is USMI diagnosed?

Answer 14

• Hx + CS suggestive of USMI
• Rule out conditions causing PD + PU
• Rule out UTI + causes of cystitis
• Imaging
• Trial medical tx

Question 15

What is medical treatment of USMI?

Answer 15

• increase urethral smooth muscle tone =
  -phenylpropanolamine / ephedrine
  -estriol (only in neutered bitches)
  -deslorelin implants
• Reduce possible contributing factors
  -weight loss if obese
  -treat secondary UTI

Question 16

What is surgical treatment of USMI?

Answer 16

• Cases where medications for USMI are ineffective / cause side effects =
  -colposuspension
  -urethropexy
  -hydraulic urethral occlude
  = move bladder cranially so bladder neck is in abdominal position, compress / kink urethra so resting urethral pressure is increased

Question 17

What is seen with ectopic ureters?

Answer 17

• Congenital anomaly - ureter bypass bladder + empty into urethra, vagina / rectum
• May also have congenital USMI pr hypoplastic bladder
• Secondary UTIs common (cystitis, hydroureter, pyelonephritis)
• Affected dogs dribble urine continually

Question 18

What dogs tend to get ectopic ureters?

Answer 18

• 80-90% unilateral
• Female : Male = 20:1
• Breeds = golden / labrador retrievers, skye terriers, siberian huskies

Question 19

What is treatment of ectopic ureters?

Answer 19

• Treat any associated UTI
• Early surgical management
  -ureteronephrectomy if normal renal function, unilateral ectopia
  -LASER ablation under urethro/cystoscopic guidance
• Incontinence may persist due to concurrent USMI

Question 20

What are causes of feline urinary incontinence?

Answer 20

• Neurogenic most common cause =
  -E.g. tail pull, sacral fracture
  -Poor prognosis if no improvement after 6 weeks
• Juvenile urinary incontinence (rare) =
  -Ectopic ureter (very rare)
  -Hypoplastic urethra/vaginal aplasia (rare)
• Iatrogenic (uncommon) =
  -eg. after perineal urethrostomy