Chapter 117: Urethra

Question 1

Urethra is innervated by which nerves?

Answer 1

hypogastric and pelvic

Question 2

Urethralis is innervated by which nerve exclusively ?

Answer 2

Pudendal nerve

Question 3

Blood supply by which artery?

Answer 3

Internal pudendal artery (prostatic, urethral and penile branches)

Question 4

Average diameter of male cat urethra?

Answer 4

0.7mm

Question 5

Average diameter of female dogs?

Answer 5

0.5cm

Question 6

MOA of calcium gluconate?

Answer 6

• Increases the threshold for cardiac myocyte depolarization, soley cardioprotective agent, does not alter serum K+ level
• DOA: 30-60mins

Question 7

most common site of male urethral obstructions

Answer 7

cd os penis

Question 8

how to improve success of urohydropulsion?

Answer 8

LA, lube, coccygeal epidural LA, different sizes of urethral catheter used

Question 9

animals only show clinical signs when urethral diameter is narrowed over what %?

Answer 9

> 60%

Question 10

urethral mucosa can regenerate in X days

Answer 10

7 days

Question 11

Which urethrostomy is most useful for revision of failed perineal urethrostomies?

Answer 11

TPU

Question 12

Most common complication from scrotal PU in a dog?

Answer 12

Persistent haemorrhage, haematuria 3-5 days postop and usually self-limiting

Question 13

common 2 complications from PU in cats?

Answer 13

Stricture and urine extravasation

Question 14

TPU - how much in mm length and mm in width to remove from cd ischium to expose urethra?

Answer 14

12mm in length and 10mm in width

Question 15

MST is prolonged if what happens prior to SEMS placement (self-expanding metallic stent)?

Answer 15

NSAID and chemo

Question 16

Most significant complication with SEMS?

Answer 16

Urinary incontinence 26%
stranguria is 2nd most common
( other complications bladder atony, recurrent obstruction and stent migration)

Question 17

Tx options for a urethral stricture?

Answer 17

• Urethrostomy proximal to site
• R and A
• Balloon dilatation
• Stent placement
• experimentally - Urethral replacement

Question 18

What is the most common complication post urethropexy/R and A?

Answer 18

Post op haemorrhage 39%

Question 19

List the layers of the urethra:

Answer 19

• Mucosa (transitional epithelium proximally, squamous distally)
• Submucosa (vascular)
• Muscularis

Question 20

Describe the muscularis layer of the urethra in the male and female dog and cat:

Answer 20

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 21

What is the urethral diameter of male cats at the level of the pre/post prostatic, bulbourethral glands and at the penile urethra?

Answer 21

-Pre/Post prostatic both 2mm
- Bulbourethral gland 1.3mm
- Penile urethra 0.7mm

Question 22

How long is the urethra in a male cat?

Answer 22

8.5 to 10.5 cm

Question 23

How long is the urethra in a male dog?

Answer 23

~25cm in a 25lb dog

Question 24

Urethral length in female dogs and cats?

Answer 24

7-10 cm

Question 25

Width of urethral lumen in female dogs?

Answer 25

0.5cm

Question 26

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

Answer 26

- Reduction in the thermoregulatory set point in the hypothalamus secondary to uremia - Or secondary to volume depletion and shock.

Question 27

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

Answer 27

- Renal decompensation within 24hr - Death 3-6 days

Question 28

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

Answer 28

Lactated ringer's solution (LRS) - give at least 15 min of fluids before anesthesia.

Question 29

List options and mode of action of each option for the treatment of hyperkalemia:

Answer 29

10% Calcium Gluconate - Increases threshold for cardiac myocyte depolarization. 0.5-1.5ml/kg IV over 5-10 min, last 30-60min IV dextrose +/- regular insulin - Drives K intracellularly by cotransport. Lasts 2-4hr Sodium Bicarbonate - Enables H ions to move extracellularly in exchange for K. Only used if severe acidosis

Question 30

What are the critical factors which effect urethral healing?

Answer 30

- 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 31

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

Answer 31

60%

Question 32

What can plain abdominal radiographs tell you for urethral lesions? What are they not good at?

Answer 32

Abnormal location of bladder, radiopaque calculi Not good for trauma (need contrast)

Question 33

What is the imaging modality of choice for urethral lesions?

Answer 33

Positive-contrast retrograde urethrography Use fluoro, balloon catheter in distal urethra

Question 34

Negative-contrast (air) urethrography is contraindicated in trauma for what reasons?

Answer 34

Rarely shows location of tears Can cause fatal air embolism

Question 35

Ultrasound of the urethra is limited to the extrapelvic portions, but can add information about what?

Answer 35

Wall thickness and mucosal surface contour.

Question 36

What is an emerging method of evaluating the urethra and treating lesions?

Answer 36

Cystoscopy/urethroscopy. -Stricture dilation, laser lithotripsy, laser ablations, submucosal collagen injections

Question 37

What type of suture should you use for the urethra?

Answer 37

4-0 or 5-0 Monocryl or PDS if concerned it will take time. Taper needle.

Question 38

What is the prognosis after urethral anastomosis?

Answer 38

Guarded - Some degree of stenosis is expected

Question 39

Male dogs most commonly obstruct where?

Answer 39

At os penis

Question 40

What type of analgesia can be used to help unobstruct a dog?

Answer 40

Coccygeal epidural