Urethra

Question 1

List the layers of the urethra

Answer 1

• Mucosa
• Submucosa
• Muscularis

Question 2

Describe the urethra muscularis in the male and female dogs and cat

Answer 2

Male dog:
- Inner longitudinal smooth surrounded by outer circumferential striated
- Smooth muscle is in the distal 2/3rds of the urethra
- Striated mostly Type II fast twitch, some Type I slow twitch

Male cats:
- 3 layers of smooth muscle - inner longitudinal, middle circumferential, outer longitudinal

Female dog:
- Three smooth muscle layers as male cats
- Smooth muscle essentially absent in terminal urethra
- Prominent sphincter of striated muscle at external urethral orifice

Female cat:
- Significantly more smooth muscle and significantly less striated urethral sphincter than female dog

Question 3

What is the urethral diameter of male cats at the level of the bulbourethral glands compared to the penile urethra

Answer 3

• Bulbourethral gland 1.3mm
• Penile urethra 0.7mm

Question 4

What is the theorised mechanism of hypothermia in cats with urethral obstruction?

Answer 4

• Reduction in the thermoregulatory set point in the hypothalamus secondary to uraemia
• Or secondary to volume depletion and shock

Question 5

What is the time frame for renal decompensation and death in aminals with complete urethral obstruction?

Answer 5

• Renal decompensation within 24hr
• Death 3-6d

Question 6

What fluid is most efficient for correcting electrolyte derangement with urethral obstruction?

Answer 6

LRS

Question 7

List options and mode of action of each option for the treatment of hyperkalaemia

Answer 7

10% Ca Gluconate
- Increases threshold for cardiac myocyte depolarisation. 0.5-1.5ml/kg IV over 5-10 min, last 30-60min

IV dextrose +/- regular insulin
- Drived K intracellularly by cotransport. Lasts 2-4hr

Na Bicarb
- Enables H ions to move extracellularly in exchange for K. Only used if severe acidosis

Question 8

List the critical factors which effect urethral healing

Answer 8

• Mucosal continuity
• Urine extravasation

If a strip of mucosa is left intact and urine is diverted, the urethral mucosa can regenerate within 7 days

Question 9

How much narrowing of the urethral lumen occurs before clinical signs occur?

Answer 9

60%

Question 10

List the options for a urethrostomy

Answer 10

• Scrotal
• Perineal
• Transpelvic
• Subpubic
• Prepubic

Question 11

How long should the incision in the urethra be for a urethrostomy?
How much contraction is expected during healing?

Answer 11

• 2.5-4cm long (approx 5-8x urethral diameter)
• Will contract by 1/3-1/2 during healing

Question 12

Hows does a continuous suture in a scrotal urethrostomy effect post-op haemorrhage?

Answer 12

• Decreases time of active haemorrhage from 4.2d to 0.2d

Question 13

What is the name of the standard cat PU technique?

Answer 13

Wilson and Harrison technique

Question 14

What ventral structures need to be transected during a cat PU?

Answer 14

• Ventral penile ligament
• Attachment of ischiocavernosus muscles

Question 15

To what level is the penis freed and the urethra incised in a cat PU?

Answer 15

To the bulbourethral glands

Question 16

What is the expected outcome after PU surgery?

Answer 16

• 12.8-25% early complications (haemorrhage, stricture, extravasation)
• Long-term complications 28% (UTI, recurrent FLUTD)
• Good long term outcome but most will require ongoing management of underlying uropathy

Question 17

What muscles are elevated in the approach for a transpelvic urethrostomy?

Answer 17

• Gracilis
• External obturator

Question 18

What muscles require elevation in the approach for a subpubic urethrostomy?

Answer 18

• Gracilis
• Adductor

Question 19

Which urethrostomy has the highest rate or morbidity and complications?

Answer 19

Prepubic
- 6/16 cats incontinent
- Significant peristomal skin irritation
- Stricture, kinking or compression or urethra

Question 20

List options for reinforcement of a tenuous urethral anastomosis

Answer 20

• Rectus abdominus flap
• Internal obturator flap
• Omentum

Question 21

What is the prognosis after urethral resection and anastomosis?

Answer 21

• Guarded - Some degree of stenosis is expected

Question 22

What is the most important factor in minimising stenosis after a urethral anastomosis?

Answer 22

Urinary diversion - either via u-cath or tube cystostomy

Question 23

What is hypospadia? What breed is overrepresented?

Answer 23

• Failure of the fusion of the urogenital folds resulting in incomplete formation of the penile urethra
• Bostron Terriers overrepresented

Question 24

What is epispadia?
What condition is often seen concurrently?

Answer 24

Failure of fusion of the dorsal penile urethra.
- May occur with concurrent bladder exstrophy (portions of bladder and abdominal wall absent and bladder appears inside-out)

Question 25

List the 2 broad types of urethral fistulas

Answer 25

- Urethrorectal - Urethrocutaneous

Question 26

List the surgical options for a double urethra

Answer 26

- Open surgical removal - Cyanoacrylate and coil embolisation

Question 27

What % of bladder and urethral tumours are malignant in dogs and cats?

Answer 27

- 97%

Question 28

What is the reported incontinence rate of dogs and cats after urethral stenting?

Answer 28

- 26% dogs - 50% cats

Question 29

List causes of urethral stricture

Answer 29

- Trauma - Obstruction - Inflammation - Malignancy - Iatrogenic surgical

Question 30

List the treatment options for a urethral stricture

Answer 30

- Urethrostomy - Resection and anastomosis - Balloon dilatation - Stent - Urethral replacement (Aortic stent graft, Rectus abdominus axial pattern flap, ileal segment, oral mucosal grafts +/- adipose-derived stem cells and polyglycolic acid scaffold)

Question 31

What breed are overrepresented for urethral prolapse? What are the surgical options? Recurrence rate?

Answer 31

English Bulldogs Sx Options: - Reduction and purse-string - Urethropexy - Resection and anastomosis Long-term recurrence 57%

Question 32

What can cause benign mass-like lesions within the urethra?

Answer 32

- Proliferative urethritis - Fibroepithelial polyps