Urolthiasis in Small Ruminants

Question 1

Most common urolith types

Answer 1

Calcium phosphate

Calcium carbonate (most common in the horse and small ruminants in some reports)

Struvite (magnesium ammonium phosphate) (rare)

Question 2

Sites of obstruction in small ruminants, pigs and cattle

Answer 2

Small ruminants: urethral process/vermiform appendage most commonly

Distal sigmoid flexure also v common

Bulls: distal signoid flexure

Pigs: Sigmoid flexure and distal penis

(Horse - may be palpable in the perineal urethra/ishial arch)

Question 3

Pre-op stableisation for urethral obstruction

Answer 3

IVFT for azotaemia/dehydration

Correction of hyponatraemia and hypochloraemia

Correction of hyperkalaemia (inconsistently present) w NaCl 0.9%, +/- 5-10% Dextrose at 0.5ml/kg

(Insulin and Ca borogluconate not mentioned)

May opt for bladder decompression with percutaneous cystocentesis or US guided catheter placement to facillitate pre-op IVFT. But has risk or rupture

Question 4

PO dietary advice to help prevent recurrence

Answer 4

Cessation of grain feeding

Feed grass hay

Ammonium chloide at high (450mg/kg) doses to acidify urine (pH<6.5) - difficult dt unpalatability

Question 5

Complications of tx for urolithasis

Answer 5

Recurrence

Dehiscence of urethral repair (esp if not sexualy rested)

Hydronephrosis and renal failure (rare)

Question 6

Px indicators for urolithiasis

Answer 6

K+ <5.5 mEq/dl

lack of free abdominal fluid

no hx of previous urethral process amputation

All good px indicators

Question 7

Tx Options for urolithiasis

Answer 7

Urethra: 1) Urethral process amputation

2) Urohydropulsion
3) Perineal urethrostomy(and its modifications/ishial)
4) Perineal urethrotomy (and ishial)
5) Penile amputation

(Infusion of Walpoles solution (50ml) into bladder percutaneously - can dissolve struvite or calcium crystals if no sx option through urinary acidification)

Bladder: 1) Cystotomy

2) Tube cystotomy
3) Bladder marsupialisation

Question 8

% of obstructions that may respond positively to urethral process amputation

Answer 8

50%

Question 9

Potential complications of catheterisation/urohydropulsion

Answer 9

Urethritis

Urethral rupture

Question 10

List 8 treatment options for obstructive urolithiasis in small ruminants

Answer 10

Urethral process amputation

Urethroscopy and laser lithotripsy

Temporary tube cystostomy

Urethrotomy

Perineal urethrostomy

Modified proximal perineal urethrostomy

Vesicopreputial anastomosis

Bladder marsupialisation

Question 11

Reported success rates of tube cystostomy alone in goats with obstructive urolithiasis (Jacobs 2019 Vet Surg)

Answer 11

83% required no additional surgical intervention

17% underwent further surgical intervention dt repeat obstructions in the form of urethrotomy

Question 12

Survival to hospitl DC reported by Jacobs 2019 Vet Surg for urethrostomy as a tx for repeat obstructive urolithiasis following tube cystostomy in goats

Answer 12

13/15

Question 13

Likely outcome with urethral process amputation for obstructive urolithiasis

Answer 13

As a first- line treatment, urethral process amputation reestablishes urethral flow enabling bladder emptying in 50-60% of small ruminants, but reobstruction occurs in 80-90% and within 36 hours in some.

Question 14

Components of Walpole solution?

What is it used for?

Answer 14

Sodium acetate

Glacial acetic acid

Distilled water

pH 4.5

Used for acidifying urine for urolith dissolution (esp struvite)

Chemical dissolution of CaCO3 uroliths is unsuccessful

Question 15

Procedure for amputation of the vermiform appendage

Answer 15

• Restrain in sitting position (flexes lumbosacral spine & makes penile extrusion much easier)
• Can do sedation or GA
• In those castrated before puberty, prepuce will be adhered to the penis. In this case the prepuce must be retracted from the penis to expose the complete urethral appendage for resection and to see the resulting urethral opening.
• The urethral appendage is frequently full of calculi and is often discolored.
• Cut with scissors

Question 16

Procedure for tube cystotomy in obstructed goats/rams

Answer 16

• Dorsal. 6cm caudal paramedian laparotomy 1 side of the sheath.
• Bladder will be v prominent/distended. May also be dark & friable. Often urine in abdomenl, even in the absence of a rent in the bladder, via diapedesis through distended bladder.
• Stay sutures (may req prior urine aspiration), perform a cystotomy, & suction urine & remove calculi. It may be repeatedly flushed and suctioned.
• Once emptied of calculi, attempt to pass polyurethane catheter normograde into urethra.
• Gently flush the urethra to establish patency (care re rupture).
• Foley catheter placed through a stab incision in contralateral caudal paramedian site; hemostat placed from peritoneum bluntly through the muscular body wall to tent the skin that is incised. Foley drawn into abdomen. Haemostat then pleated through omentum 3–5 X, & the tip of the Foley is pulled through the omentum.
• Cystotomy may be closed before or after placement of the Foley in the bladder,
• Cystotomy closed w 2-0 absorbable suture in a simple continuous (not penetrating bladder lumen) w inverting oversew.
• Purse-string suture placed on ventrolateral aspect of the bladder on the contralateral side to the original body wall incision.
• Stab incision made inside purse string, & Foley inserted before tightening & purse string.
• Foley balloon filled w saline & positioned at the bladder wall. Exterior portion of catheter is retracted so intra-abdominal is straight but not under tension.
• Catheter secured to body wall (finger trap) and routine abdominal incision closure
• A finger of a sx glove with a hole in tip may be taped to end of catheter as 1-way valve