Urolithiasis in sheep, goats and cattle

Question 1

how do uroliths cause disease?

Answer 1

Urinary calculi, or uroliths, cause disease in ruminants through obstruction and trauma to the urinary tract

Question 2

anatomy of ruminant penises, some common sites for uroliths

Answer 2

• Fibroelastic penis is rigid even when not erect
• Smaller urethra relatively than horses or dogs
• Sigmoid flexure – caudal to scrotum, common site for obstruction
• Diameter of urethra narrows as it courses from proximal to distal
• In sheep and goats a urethral process is present, which is a common site for calculi to lodge and it ss common for multiple calculi to lodge at one or more sites

Question 3

Where do calculi lodge?

Answer 3

• Urethral process
• Sigmoid flexure
• Distal end of urethra
• Anywhere along urethra

Question 4

urolithiasis presurgical considerations
- Anesthesia/analgsia and restraint

Answer 4

Anesthesia/analgsia and restraint
* Usually surgery done standing in cattle
* Caudal epidural
* Sedation only if needed (may go down if too much given)

Question 5

presurgical considerations for sheep and goats
- position, anesthetic

Answer 5

• Dorsal recumbency
• Sedation or general anesthesia

Question 6

different approaches for surgery based on intended use of animal?

Answer 6

Feedlot steer – find exit for urine
until slaughter
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Breeding bull – provide exit for urine (temporary), remove obstruction stone, preserve breeding function
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Pet goat/sheep:
* Provide exit for urine
* Temporary to allow medical treatment to remove stone
* Permanent if recurrence or stone cannot be removed

Question 7

Goals of surgery, in order:

Answer 7

*Re-establish urine flow (permanent or temporary)
*Remove the urethral obstruction (calculi/calculus)
*Preserve penis function

Question 8

options for surgical techniques

Answer 8

• Amputation of urethral process
• Urethrotomy/urethrostomy
• Catherisation

Question 9

Amputation of urethral process
- how to perform
- indications
- observations after?
- effects on repro?

Answer 9

Exteriorise with sheep/goat on rump, sedated, with topical lidocaine
* Can be challenging to
exteriorise
* Cut process with Mayo scissors
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* Usually first line to relieve obstruction
* common site of obstruction & a simple step to take
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* Look for full stream of urine after to ensure there are not more stones obstructing sigmoid flexure
* Does not affect reproductive ability of rams

Question 10

Perineal urethrotomy or perineal urethrostomy
- approaches? difference between these?

Answer 10

o high approach vs low approach
o temporary exit of urine (urethrotomy) vs permanent exit (urethrostomy)
o any combination of above can be used with appropriate indications/considerations

Question 11

PU: high vs low approach
- where
- indications

Answer 11

• High = ischial arch
• UrethroStomy by penile amputation
• can be good for multiple (“sand”) calculi
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• Low = caudal to scrotum
• Urethrotomy to remove calculi
• Urethrostomy with penile amputation for permanent exit of urine

Question 12

PU: low approach pros and cons

Answer 12

Advantages:
- penis superficial and easier to exteriorise
- exposed sigmoid flexure - a site of urinary obstruction
- less skin irritation
- low in urethra - can be repeated
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Disadvantages:
- More awkward for surgeon
position in standing cattle
- Obstruction may be proximal to this site (determine with ultrasound/ radiographs/ contrast study before starting)

Question 13

PU: high approach pros and cons

Answer 13

Advantages
* Position is proximal to all
urethral obstructions
* Sheep/goats often have accumulations of stones/sand proximal to sigmoid flexure, therefore accessible by this approach
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Disadvantages
* Calculi usually distal to this
position therefore not accessible
* Penis can be deep at this location and difficult to identify and exteriorise
* Urine scalding more likely than distal approach due to higher position

Question 14

• urethrotomy (temporary) surgical approach
• disadvantages

Answer 14

–usually low over sigmoid flexure, caudal to scrotum
* Can be used to provide temporary exit of urine if left open (healing by 2nd intention)
* Can be used specifically for removal of urinary calculi (sutured closed)
* Can preserve function of penis in breeding bull
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Disadvantages
* Stricture formation in goats/sheep, leading to repeat obstruction
* Procedure can be technically challenging

Question 15

UrethroStomy by penile amputation – permanent
- Advantages of penile amputation include:

Answer 15

• easier exteriorisation of penis and anchoring of urethra to skin incision
• Distal penis often of no functional use due to obstruction or rupture

Question 16

Permanent PU
- surgical approach?
- when we do this?

Answer 16

o Surgical approach: can use low or high approach, but low preferred
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§ Commonly used:
* For obstruction with or without urethral rupture
* Provides permanent exit for urine
* if urethral rupture

Question 17

UrethroStomy by penile amputation – permanent
- surgical technique

Answer 17

• Dissect, mobilize & exteriorize sufficient penis so that it easily remains at the skin surface.
• Ligate dorsal vessels of penis with “stick tie”, proximal & distal to amputation site
• Amputate penis proximal to the site of urethral rupture or calculus lodgement.
• Fixation of penis/urethra to skin
  > Fast method: Place a big horizontal-mattress suture that passes through each side of the skin incision & through the corpus cavernosum of the penis
  > Best method– spatulate urethra and suture edges of urethra to
  edges of skin incision

Question 18

complications of urethrostomy?
where is it common?

Answer 18

• Greater chance of urethral obstruction at amputation site
• Beware of accidentally suturing through the urethra
• failure, bleeding
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• Commonly performed in feedlots

Question 19

catheterization of bladder - issues going retrograde up the urethra

Answer 19

Challenges in getting to bladder:
* Exteriorising penis
* Sigmoid flexure
* Urethral diverticulum
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- almost impossible to pass

Question 20

tube cystotomy - when we use it?

Answer 20

• Sheep & goats (usually pets or valuable breeding animals) with urethral obstruction not relieved by urethral-process amputation
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• In sheep & goats, urethrotomy & urethrostomy have guarded prognosis,
  due to stricture formation & repeat urethral obstruction in ≥ 50% of cases

Question 21

Tube cystotomy
- how we perform it
- purpose

Answer 21

• Catheter placed via paramedian laparotomy & cystotomy
• Catheter provides temporary exit for urine
• Allows prolonged medical treatment of urethral obstruction

Question 22

ruptured bladder - what we do ideally, and what actually happens
- how?

Answer 22

• Surgical repair of ruptured bladder
• Ideally, ruptured bladder is surgically repaired → indwelling urinary catheter
  keeps the bladder decompressed → aids healing
• Due to economics, surgical repair of a ruptured bladder is rarely performed in cattle, sheep or goats, unless they are pets or valuable breeding animals.

Question 23

ruptured bladder aftercare

Answer 23

Perioperative medication
o Systemic antibiotics?
o Analgesic/anti-inflammatory medication (NSAIDs)
o Tetanus prophylaxis?
o Additional medical therapy
1. To treat any additional existing calculi
2. To prevent formation of new calculi