Ch 117 - Urethra Flashcards

1
Q

List the layers of the urethra

A
  • Mucosa
  • Submucosa
  • Muscularis
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2
Q

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

A

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

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3
Q

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

A
  • Bulbourethral gland 1.3mm
  • Penile urethra 0.7mm
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4
Q

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

A
  • Reduction in the thermoregulatory set point in the hypothalamus secondary to uraemia
  • Or secondary to volume depletion and shock
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5
Q

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

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

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

A

LRS

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7
Q

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

A

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

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8
Q

List the critical factors which effect urethral healing

A
  • Mucosal continuity
  • Urine extravasation

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

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9
Q

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

A

60%

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10
Q

List the options for a urethrostomy

A
  • Scrotal
  • Perineal
  • Transpelvic
  • Subpubic
  • Prepubic
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11
Q

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

A
  • 2.5-4cm long (approx 5-8x urethral diameter)
  • Will contract by 1/3-1/2 during healing
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12
Q

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

A
  • Decreases time of active haemorrhage from 4.2d to 0.2d
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13
Q

What is the name of the standard cat PU technique?

A

Wilson and Harrison technique

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14
Q

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

A
  • Ventral penile ligament
  • Attachment of ischiocavernosus muscles
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15
Q

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

A

To the bulbourethral glands

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16
Q

What is the expected outcome after PU surgery?

A
  • 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
17
Q

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

A
  • Gracilis
  • External obturator
18
Q

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

A
  • Gracilis
  • Adductor
19
Q

Which urethrostomy has the highest rate or morbidity and complications?

A

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

20
Q

List options for reinforcement of a tenuous urethral anastomosis

A
  • Rectus abdominus flap
  • Internal obturator flap
  • Omentum
21
Q

What is the prognosis after urethral resection and anastomosis?

A
  • Guarded - Some degree of stenosis is expected
22
Q

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

A

Urinary diversion - either via u-cath or tube cystostomy

23
Q

What is hypospadia? What breed is overrepresented?

A
  • Failure of the fusion of the urogenital folds resulting in incomplete formation of the penile urethra
  • Bostron Terriers overrepresented
24
Q

What is epispadia?
What condition is often seen concurrently?

A

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)

25
Q

List the 2 broad types of urethral fistulas

A
  • Urethrorectal
  • Urethrocutaneous
26
Q

List the surgical options for a double urethra (urethral duplication)

A
  • Open surgical removal
  • Cyanoacrylate and coil embolisation
27
Q

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

A
  • 97%
28
Q

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

A
  • 26% dogs
  • 50% cats
29
Q

List causes of urethral stricture

A
  • Trauma
  • Obstruction
  • Inflammation
  • Malignancy
  • Iatrogenic surgical
30
Q

List the treatment options for a urethral stricture

A
  • 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)
31
Q

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

A

English Bulldogs

Sx Options:
- Reduction and purse-string
- Urethropexy
- Resection and anastomosis

Long-term recurrence 57%

32
Q

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

A
  • Proliferative urethritis
  • Fibroepithelial polyps