Urethral sphincter mechanism incontinence

Question 1

In a study by Bohlen 2022 in JSAP, what percentage of male dogs with USMI had long-term continence improvement with placement of an artificial urethral sphincter? What was the complication rate, and list 3 minor and 3 major complications?

Answer 1

60% of dogs showed long-term improvement, with 53% completely continent.

Overall complication rate of 56%.

Minor complications (25%) included haematoma, stranguria/temporary dyssynergia, mild inflammation at the port.
Major complications (31%) included stranguria/mechanical urethral obstruction, persistent dyssynergia, fistula at the port and port rotation.

Question 2

In a study by Kopecny 2022 in JVIM, what complication resulting in urethral obstruction occurred secondary to placement of an artificial urethral sphincter device for urinary incontinence in 5 dogs?

Answer 2

Capsule formation. Surgical removal resulted in resolution of obstruction, but recurrent incontinence in some dogs. Cultures collected at the time of surgery were all positive for growth (see image).

Question 3

In a study by Hooi 2022 in JVIM, what percentage of dogs were considered continent after cytoscopic guided laser ablation of intramural ectopic ureters? What percentage of dogs had additional medical management?

Answer 3

68% of dogs were considered continent.

55% of dogs had additional medical management.

Question 4

In a study by Vaden 2022 in JVIM, what novel technique was used for the treatment of urethral sphincter mechanism incontinence in female dogs?

Answer 4

Injection of autologous muscle progenitor cells collected from the triceps muscle. All but 2/15 dogs required ongoing medical management, but improvements in continence were observed.

Question 5

What are factors that contribute to urinary continence in the dog?

Answer 5

Tone in the urethral smooth muscle (most prevalent in the cranial 50% of the urethra), tone in the striated muscle (caudal third of the urethra), the natural elasticity of the urethral wall tissues, and physical properties of the urethra (length and diameter, pelvic diaphragm muscle mass).

Question 6

What are some factors that might predispose to development of USMI?

Answer 6

1. Urethral tone and length.
2. Bladder neck position.
3. Body size and breed.
4. Gonadectomy.
5. Hormonal status.
6. +/- Genital conformation.

Question 7

How is urethral tone and length thought to contribute to development of USMI?

Answer 7

Decreased length and tone may predispose to leakage during elevation of intra-abdominal pressure.

Tail docking has been associated with USMI possibly due to atrophy of the pelvic muscles, which may aid in providing external pressure to the distal urethra.

Question 8

How is bladder neck development thought to contribute to development of USMI?

Answer 8

Pelvic bladder may reduce the conveyance of abdominal pressure to the urethra and may also reduce total urethral length.

Question 9

How is body size and breed thought to contribute to development of USMI?

Answer 9

Large and giant breed dogs are seven times more likely to develop incontinence. Obesity may worsen clinical signs.

Question 10

How is gonadectomy thought to contribute to development of USMI?

Answer 10

Risk of USMI is 8 times higher in spayed than intact dogs. Females spayed before 3-months of age may be at increased risk.

Spaying may cause a reduction in muscle and increase in collagen within the lower urinary tract.

Question 11

How is hormonal status thought to contribute to development of USMI?

Answer 11

Elevated LH and FSH after gonadectomy may contribute to USMI, with an injection of GnRH shown to improve symptoms. Decreased COX-2 expression may also reduce production of prostaglandins (although exact role uncertain). Reductions in estrogen cause lower urethral smooth muscle tone.

Question 12

Does genital conformation contribute to development of USMI?

Answer 12

Vestibulovaginal stenosis has been previously linked to urinary incontinence due to the tendency of urine to accumulate cranial to the stenosis, however it is now thought that this may be unrelated and that if underlying USMI is treated concurrent stenosis is irrelevant.

The signs associated with recessed vulva may also be confused with urinary incontinence in some cases.

Question 13

What is the most common cause of congenital USMI in male dogs?

Answer 13

Prostatic or pelvic urethral abnormalities (urethral dilatation or prostatic diverticula).

Question 14

What baseline diagnostics are recommended in the work-up of USMI?

Answer 14

CBC/biochem, urinalysis + culture, digital rectal examination, and vestibular examination.

CT excretory urography or endoscopy, should be considered in patients who have been incontinent since birth or are suspected of having other complicating conditions.

Question 15

What are medical management options for USMI?

Answer 15

1. Sympathomimetic agents: phenylpropanolamine (alpha-adrenergic agonist).
2. Parasympatholytic agents
3. Estrogen supplementation (in spayed dogs).
4. GnRH analogues (reduce FSH and LH).

Question 16

In what percentage of juvenile dogs does urinary incontinence resolve after the first heat?

Answer 16

50%

Question 17

What is the expected cure rate of USMI with single therapy treatment?

Answer 17

50%

Question 18

What are surgical options for management of USMI?

Answer 18

1. Colposuspension
2. Urethropexy, cystourethropexy
3. Bulking agents
4. Transpelvic urethral sling
5. Transobturator vaginal tape
6. Artifical urethral sphincter

Question 19

How is colposuspension performed?

Answer 19

The vagina is anchored with sutures to the prepubic tendon, increasing the functional urethral length. Goal is to restore normal intraabdominal pressures across the proximal urethra and bladder neck.

Question 20

How many sutures should be placed between the vaginal and prepubic tendon during colposuspension?

Answer 20

2 on each side (only 1 may be possible in small dogs).

Care must be taken not to compress the urethra against the pubis as this may result in dysuria.

Question 21

What is the success rate for continence after colpsuspension?

Answer 21

53-55%, relapse is possible in 11%.

Acquired USMI may respond more favorably than congenital USMI to this technique.

Question 22

What is the objective of urethropexy and cystourethropexy?

Answer 22

To relocate the bladder neck into a more cranial intraabdominal position. An increase in urethral resistance may also occur secondary to slight kinking at the level of pexy.

Both procedures are similar, but cystourethropexy results in placement of more sutures to include the bladder neck.

Question 23

What is the success rate for urethropexy and cystourethropexy?

Answer 23

56% when performed as the sole procedure. 70% cure rates have been reported when combined with colposuspension.

Question 24

What are complications associated with urethropexy and cystourethropexy?

Answer 24

Reported in 21% of dogs, including dysuria, anuria and pollakiuria.

Question 25

Why is cystopexy alone contraindicated for the treatment of USMI?

Answer 25

May cause detrusor instability, worsening clinical signs.

Question 26

What is the preferred material for submucosal urethral injection of a bulking agent?

Answer 26

Bovine cross-linked collagen.

Typically three injections are required (to create apposition).

Question 27

What is the major complication associated with transpelvic urethral sling?

Answer 27

Development of fistulas secondary to the ribbon.

The technique is similar to the transobturator vaginal tape and involves passage of a ribbon around the mid-urethra and obturator foramen, before being secured with a titanium Ligaclip.

Question 28

What device is shown in the image?

Answer 28

Transobturator vaginal tape. Placed using an inside-out technique which minimizes the number of complications and amount of dissection required.

Question 29

What complications are reported with the use of transobturator vaginal tape?

Answer 29

Post-operative dysuria (33%), and fistula formation.

Question 30

What device is shown in the image?

Answer 30

Question 31

In what portion of the urethra should artificial urethral sphincters be placed?

Answer 31

2cm caudal to the bladder to prevent ureteral obstruction in females, 1cm caudal to the prostate in males.

Question 32

How is the size of the artificial urethral sphincter selected?

Answer 32

Should be 50% of the circumference of the urethra (10 mm device for 20 mm urethra).

Question 33

How long after surgery should injection be delayed in an artificial urethral sphincter device?

Answer 33

6-weeks to allow for resolution of inflammation and revascularization of the periurethral tissue.

Question 34

What is the success rate of artificial urethral sphincter placement for USMI?

Answer 34

33-45% of dogs are continent with placement of the sphincter alone, with the remaining dogs requiring 1 or more saline infusions and ongoing medical management (36-56% complete continence rate).

Question 35

What are some potential complications associated with use of an artificial urethral sphincter for USMI?

Answer 35

Urethral obstruction (7-17%), UTI (63%), infection of the port site, accidental puncture of the device, delayed urethral obstruction necessitating removal.

Question 36

Is treatment of USMI in males typically more or less effective than in females?

Answer 36

Less effective (<50% resolution in most cases).

Medical management typically involves alpha adrenergics.