CS: Urolithiasis

Question 1

CS - upper urinary tract uroliths

Answer 1

• variable
• haematuria
• CS compatible with acute kidney injury secondary to ureteral obstruction

Question 2

Normal canine USG

Answer 2

1.015 - 1.045

Varies with fluid intake, hydration

Question 3

Normal feline USG

Answer 3

1.035-1.060

Varies with fluid intake, hydration

Question 4

What are the 2 most radioopaque crystals

Answer 4

calcium oxalate and struvit

Question 5

What urine pH favours struvite and calcium oxalate formation?

Answer 5

• STRUVITE: alkaline

- CALCIUM OXALATE: acidic to neutral

Question 6

T/F: uroliths >1cm likely to be struvite

Answer 6

True

Question 7

T/F: sterile struvite uroliths rarely form in dogs

Answer 7

True - common in cats

Question 8

Why do you need a stone sample?

Answer 8

detect what mineral type and whether different mineral layers are present.

Question 9

What should you do if urine culture is negative in a dog with struvite uroliths?

Answer 9

the stone and/or bladder mucosa can also be cultured to be certain that a bacterial pathogen is not present

Question 10

What is medical management of struvite sotnes?

Answer 10

dissolution and prevention of stone reformation (aim to reduce concentrations of ammonium, magnesium and phosphate in urine

Question 11

Advantages - sx tx of struvite bladder stones

Answer 11

 Most direct

 Healing may commence say day

Question 12

Disadvantages - sx tx of struvite bladder stones

Answer 12

 Those inherent to sx (anaesthetic risk, post-op pain)
 Risk of contaminating abdomen with infected urine
 Incomplete removal nidus for recurrence
 Bladder stitches not holding

Question 13

Indications - sx removal of struvite bladder stones

Answer 13

• immediate/ emergency removal (e.g. blocked animal)

Question 14

What is VUH?

Answer 14

= voiding urohydropulsion

• anaesthesia
• for small stones
• fill bladder via urinary catheter (sterile saline), agitating bladder so stones float freely in urine. Hold animal upright, remove catheter, then generating a high pressure urine stream to force stones out

Question 15

What is cystoscopy?

Answer 15

• if stones small enough and avoiding sx is key

- cystoscope passed into bladder and stones retrieved with special basket (or fragmented via laser lithotripsy)

Question 16

Advantages/ disadvantages of cystoscopy

Answer 16

o DISADVANTAGES: Special equipment, referral, generally more expensive than sx
o ADVANTAGES: recovery much faster

Question 17

Outline medical management of struvite bladder stones

Answer 17

• dietary
  o Uroliths should decrease in size within 3-4 weeks (if good owner compliance)
  o Only feed until stone dissolved
  o ABs needed as long as stones present in bladder (bacteria encrusted in stone and as stone dissolves they are released).

Question 18

Reasons for tx failure when medically managing struvite bladder stones

Answer 18

• poor compliance with diet / ABs

- stone has layers of calcium phosphate in form of appatite or may not contain struvite

Question 19

Disadvantages - medical management of struvite bladder stones

Answer 19

o DISADVANTAGES: long tx time, possibility of UT obstruction as stone gets smaller, v high in fat and salt and low in protein (not for patients with hx of pancreatitis, heart disease, kidney insufficiency or high BP)

Question 20

CI - medical management of struvite bladders stones

Answer 20

urethroliths causing obstruction or if patient’s CS are severe.

Question 21

Prevention - struvite stones

Answer 21

• high moisture diets

that produces a urine pH

Question 22

What is a typical crystal appearance for ammonium urate?

Answer 22

‘thorn-apple’ appearance

Question 23

Why is it often not possible to count the # of urate stones?

Answer 23

there are so many and range in size from grain of sand to ball bearing

Question 24

How do you image a dalmation’s bladder after urate stone removal?

Answer 24

• ULTRASOUND as urate stones are radiolucent to faintly radioopaque so unlikely to be detected with radiography

Question 25

What is the medical management for urate bladder stones?

Answer 25

• Allopurinol for dissolution for 4 weeks (this reduces uric acid)
• DIET: low protein, high moisture, urine-alkalising, high value protein
• CI: GCs, immunosuppressive drugs, renal failure, PSS

Question 26

Why may xanthine stones form treating urate stones with allopurinol?

Answer 26

Because xanthine is a metabolite in the pathway to uric acid. Allopurinol stops this pathway to reduce the amount of uric acid (and hence reduce urate stone formation) but increases the amount of xanthine metabolite hence potentially causing xanthine stones. TO prevent keep on the low protein, high moisture diet.

Question 27

What is detected in genetic tests for dalmations with tendency of forming urate stones?

Answer 27

• SLC2A9 gene is mutated in dalmations (this causes altered transport of uric acid in hepatic/ renal transport)
• homozygous recessive mutation
• buccal swab to collect DNA

Question 28

What is recurrence rate of urate crystals?

Answer 28

variable, 33-50%

Question 29

How to monitor efficacy of urate stone medical management?

Answer 29

• UA every 3 months

- imaging every 6 months

Question 30

T/F: all damations are homozygous recessive for hyperuricosuria

Answer 30

True

Question 31

What are low uric acid dalmations?

Answer 31

when a purebred dalmation has been crossed with another breed

Question 32

How to reduce prevalence of urolithiasis in dalmations

Answer 32

• Increase water intake
• Low protein low purine diet
• Let outside regularly to toilet
• Exercise to prevent stagnant urine
• Allopurinol (competitive inhibitor of xanthine oxidase)